The Distribution Pattern and Spatial Morphological Characteristics of Military Settlements Along the Ming Great Wall in the Hexi Corridor Region

Abstract

Military settlements along the Ming Great Wall are typical representatives of the construction of the ancient Chinese military defense system. The location of the military fortification is complex, and the settlements are scattered and affected by multiple factors. The academic community lacks systematic research on the military settlements along the Ming Great Wall. Existing studies focus on local protection, especially the regional connectivity and overall defense mechanism of the military settlements in the Hexi Corridor. This study incorporates the distribution, morphology, and function of the military settlements in the Hexi Corridor into a unified analytical framework to explore the coordinated defense mechanism under the spatial attributes of the military settlements. Additionally, this study looks at the distribution pattern of 173 local military settlements using tools such as the kernel density index, the Moran index, and the buffer zone. It also conducts statistical analyses of 85 existing settlements to determine their scale and morphological index and uses 18 typical settlements as examples to investigate their spatial morphology using space syntax. This study’s findings indicate that (1) military settlements are spread out in a straight line, which is affected by many things such as terrain, water systems, oasis, and the Great Wall; (2) military facilities and environmental factors are strongly connected and linked in space; (3) military settlements have obvious cluster characteristics, and most are relatively regular quadrilaterals; and (4) the organizational logic of the internal space form is consistent. The main blocks are highly accessible, and the overall space is recognizable and has certain defensive characteristics. This study systematically constructed an analytical framework for multi-scale collaborative defense mechanisms, revealing a collaborative defense model of “linear distribution–hierarchical defense–functional coordination”. This demonstrates the top–down strategic thinking of the ancient Chinese military system and provides a new perspective for the study and protection of linear military heritage corridors.

1. Introduction

A large number of military fortifications are listed as World Heritage around the globe, and their protection is conducive to promoting sustainable development [1]. Goal 11.4 of the 2030 Agenda for Sustainable Development clearly states that efforts should be made to protect and preserve the world’s cultural and natural heritage [2]. East Asian architectural heritage is highly concentrated in China [3]. Natural erosion and human activities have caused irreversible damage to many architectural sites [4]. According to China’s third national cultural relics survey, over 40,000 immovable cultural relics have disappeared in the past 30 years, and half of the architectural projects have been destroyed [5]. The Great Wall is China’s largest existing cultural heritage and a spiritual symbol of the Chinese nation. As a typical representative of the world’s linear military heritage, the Ming Great Wall military settlement system has dual value in cultural heritage protection and historical geography research. In December 1987, the Great Wall was listed as a UNESCO World Heritage Site [6]. Since 1961, China has continuously strengthened its protection of the Great Wall and expanded it to cover surrounding military settlements. In 2019, the National Culture Heritage Administration and the Ministry of Culture and Tourism of the People’s Republic of China jointly issued the General Plan for the Protection of the Great Wall, which clearly stated that the Great Wall’s cultural relics include the walls, individual buildings, forts, related facilities, and other types of remains [7].

The Great Wall of the Ming Dynasty (A.D. 1368–1644) is the world’s largest, most widely distributed, and longest-built ancient military defense system. The agricultural and pastoral transition zone is predominantly in northern China [8]. The Hexi Corridor has been plagued by wars since ancient times. It is a complex linear corridor where multiple cultures collide and commercial trade occurs [9]. The region is rich in military resources and has significant environmental characteristics. Due to the scattered geographical distribution of local military settlements and their distance from the city center, a large number of settlements are still in the protection blind spot. In the increasingly accelerated urbanization process, the destruction and disappearance of immovable cultural heritage, such as military relics and traditional buildings, have blurred the spatial order of military settlements, making characteristic analysis more difficult. The building of the defense system and the characteristics of military culture within their internal area have likewise vanished.

Current research focuses on protecting the Great Wall in local areas [10,11]. There is a lack of systematic research on military settlements along the Hexi Corridor, resulting in two key academic gaps: in terms of the regional dimension, existing research results are mostly concentrated on the coastal areas of Jiangsu and Zhejiang [12,13,14] and the Beijing–Tianjin–Hebei region [15,16], while ignoring the military geographical characteristics of the arid and semi-arid areas of the northwest; in terms of methodology, existing research presents a scale split of “macro-distribution and spatiotemporal evolution [17]-micro-architectural defense [18,19,20]”, lacking a coherent study of the spatial form of settlements at the meso level. This limitation has long left the “environment-space-military” synergistic mechanism of military settlements in a theoretical black box state. Therefore, this study uses 173 Ming Dynasty military settlements in the Hexi Corridor as a sample and multi-scale spatial analysis to solve three core problems: (1) How does the spatial distribution of settlements respond to environmental factors to form a defense network? (2) How do we analyze the internal spatial form and functional layout of military settlements; what is the spatial correlation between the spatial form and functional layout of military settlements? (3) How does the multi-scale spatial layout of military settlements construct its synergistic defense mechanism and reflect the connotation of the city-building culture?

The innovation of this study lies in (1) systematically revealing the coupling law between military settlements and environmental factors in the Hexi Corridor and proposing a military defense system model of “linear distribution–hierarchical defense–functional coordination”; (2) constructing a multi-scale research method of “macro-distribution pattern–meso-spatial form–micro-functional organization”, providing a generalizable analytical framework for the protection of linear heritage corridors; and (3) verifying the spatial paradigm inheritance of the square city system in the construction of Chinese military settlements through quantitative analysis, and deepening the understanding of ancient military strategic wisdom.

2. Literature Review

2.1. Review of Military Defensive Settlement Studies

Military defensive settlements are strategic stronghold systems built with military defense as their core function and in combination with terrain conditions. They are characterized by clear defensive boundaries and hierarchical defensive facilities [21]. Early research on military defensive settlements focused on castle architecture. In 1925, Belgian historian Henri Pirenne first focused his research on defensive castle architecture and elaborated on the layout characteristics of defensive settlements in the West during the Middle Ages [22]. He pointed out that cities are settlements centered on towns and fortresses that defend local areas and carry out commercial activities [23]. British architectural historian Oliver Paul (1997) analyzed the specific connotation and use of “territory” from a multi-dimensional perspective and pointed out that boundary facilities achieve the construction of psychological security through the declaration of spatial sovereignty [24]. In the 1990s, De Blij Harm J. and Murphy Alexander B. (1999) divided settlements into five categories: linear village, cluster village, round village, walled village, and grid village, emphasizing the defensive advantages and security of circular layouts [25]; this formed a dialog between Eastern and Western theories with the idea that the “square is good for defense”, proposed by Chinese scholars [26,27]. Chinese scholars Zhang Yukun and Song Kun (1996) studied the “fort”-shaped settlements in Shanxi Province and explained their spatial correlation with the ancient Chinese Lifang system [28]. Kaufmann, J.E. et al. (2001), medieval historians, looked at the building and changes in defensive castles in many medieval countries from a military point of view. They also looked at what the defense system was made of and why it fell apart [29].

In recent years, the research direction of military defensive settlements has expanded. It mainly focuses on the following aspects: function and element analysis at the micro-scale, settlement classification research at the meso scale, and distribution pattern and influencing factors research at the macro scale.

(1)

This study focuses on function and element analysis at a micro-scale. Many researchers have looked at how military bases are spread out in space [30], how they are organized functionally [31], and how they are protected [32,33] using landscape genes [34], typological research [35], and historical data analysis. This type of research explores settlements’ internal organization and landscape characteristics at a micro-scale and can simplify and extract the complex elements that make up a settlement. However, reliance on formal features may separate them from factors such as function, and subjective judgment may also affect the extraction of features and elements.

(2)

This study focuses on the morphology of settlements and their classification at the meso scale. Much research has put military settlements into different types [36] based on how well they defend [37], how they change over time and space [38], where they are located [39], and the shape of the settlements [40,41]. Multi-dimensional classification studies help to reveal the inherent laws of settlement construction and provide a classification framework for systematic research and cross-regional comparison. However, the subjective nature of the criteria used to classify settlements is a big part of how they are put into groups. Additionally, focusing only on how a settlement looks from the outside can make it easy to forget about its social structure, cultural traits, and economic activities that happen inside it.

(3)

Extensive research has been conducted on the distribution pattern and the factors that influence it on a macro scale. Using the theories of military geography [42], fractal geometry [15,43], landscape ecology [26], and archeology [44], many researchers have looked at how military settlements are spread out in space and how military defense systems are built in response to related factors [45,46]. Their research methods have transformed from the initial field survey to combined methods such as GIS spatial analysis and spatial statistics. Because of this, the study of where settlements are located and the factors that affect them has changed from a qualitative to a quantitative approach. The superior version of this analysis method makes it easier for researchers to understand how military settlements are spread out overall, which helps them figure out what their defense system is like. Quantitative analysis has made this part of the research more accurate. The above research perspectives have profound guiding significance for this study. However, a single qualitative analysis makes the research subjective and imprecise and may lead to neglecting the historical, cultural, and social factors behind it regarding constructing theoretical frameworks and evaluating variable relationships.

Military settlements or castles have been widely studied by scholars from various countries since the end of the 20th century. Architecture, planning, landscape ecology, and archaeology play a role in military settlement research, which is split into three levels: macro, meso, and micro. Each level provides a different research perspective. Most studies only examine one or two of them, and most are qualitative. It is hard to fully understand military settlements because different fields do not work together. Also, the research is inaccurate or unscientific because it only uses one type of method, especially since modern technology does not use quantitative methods.

Table 1. The research focuses on military defensive settlements.

Research Focus	Year	Research Object	Key Findings	Research Methodology	Limitation
Function and element analysis	2003	Fortress settlements in Shanxi, China	The defensive settlement is divided into three levels of defense structure from the outside to the inside: outer city wall–street passage–residential unit, and has multiple functions.	Qualitative research	It focuses on extracting settlements’ form and function characteristics, which are easily affected by individual subjectivity. In addition, this reliance on feature extraction may lead to the separation of form and function analysis.
	2019	Six coastal defense settlements in China during the Ming and Qing dynasties	Through the landscape gene theory, the characteristics of the internal landscape elements of the coastal defense settlement are analyzed, including city walls, building orientation, and religious and ancestral halls.	Qualitative research
	2022	Dastkand, an ancient underground fortification in Iran	The ten core elements of Dastkand’s defense space are revealed through factor analysis.	Mixed qualitative and quantitative research
	2022	The medieval castle of San Salvador de Todea in northwestern Spain	Through its virtual reconstruction, it is shown that the construction of towers and ramparts and the multi-level spatial division are important means to achieve control of the surrounding landscape and strategic defense.	Qualitative research
	2022	Seb Castle in Saravan County, Iran	The construction of its defensive space has clear functional divisions and multiple spatial connection methods. This layout fully considers the defense needs and residential functions.	Qualitative research
Settlement classification research	2006	A study of China’s defensive settlement system	According to the characteristics of fortification, Chinese defensive settlements are divided into two categories: peripheral linear fortification and local point fortification, and the former is divided into community form and single form. It establishes a type framework for the study of traditional Chinese defensive settlements.	Qualitative research	The subjectivity of settlement classification research is a key factor that affects the analysis results. At the same time, excessive attention to the external appearance of settlements can easily lead to the neglect of their internal connections, such as social structure, cultural characteristics, and economic activities.
	2017	The spatiotemporal evolution of 13 fortress settlements at the border of Shanxi and Inner Mongolia, China	Historical data and field research divide it into three types according to the evolution of time and space: development of the original site, expansion of spatial boundaries, and abandonment of the original site and relocation. It also reveals the economic and social internal causes of its evolution.	Qualitative research
	2020	Landscape characteristics of 459 medieval to modern castles worldwide	Through k-means clustering and principal component analysis, a typological study is carried out, and eight castle patterns are proposed.	Quantitative research
	2022	Classification of military settlement site types in the Ming Dynasty in Guizhou Province, China	This study summarizes the site selection distribution of settlements based on terrain and water systems and divides settlements into flat land, valleys, and slopes. According to function, settlements are divided into two types: transportation type and lookout type.	Qualitative research
	2023	Morphological structure classification of six bastion castles in Poland	This study divides castles into integrated and compound structures, and their subtypes are based on morphology and functional layout.	Qualitative research
	2024	Rammed earth buildings of defensive settlements in Fujian, China	From the perspective of architectural typology, the defensive buildings in Fujian are divided into three types: Tulou, Tubao, and Zhailu. It points out the homology of architectural form, cultural connotation, and the difference between defensive and residential functions.	Qualitative research
Study on distribution patterns and influencing factors	2008	Song Dynasty Forts in Northern Shaanxi, China	Based on field research, 117 Song Dynasty forts in northern Shaanxi were counted, and the distribution location and preservation status of some of them were introduced. This study shows that forts are distributed in places with important transportation routes, fertile soil, and complete water systems.	Qualitative research	The research accuracy of a single qualitative analysis is low; a single quantitative analysis may lead to excessive focus on quantitative data and ignore the influence of deep-seated internal factors.
	2013	Defensive villages and fortified farms in seven areas of the late Roman frontier in North Africa	GIS methods and archeological analysis reveal the influence of terrain factors such as mountain tops, heights, and steep slopes on the distribution of villages and farms.	Quantitative research
	2019	Military castles in England from the 11th to 14th centuries	Through GIS methods and archeological analysis, this study reveals the spatial coupling between castle distribution and ancient relics under the influence of multiple factors such as society, politics, and culture.	Quantitative research
	2020	Ancient houses, fortress-village, towns, and cities in China	From the perspective of landscape ecology and archeology, through field research and GIS visualization analysis, the site selection considerations for large-scale and medium-scale forts are explained, respectively, including social politics, regional topography, ecological environment, and people’s physical and mental perception.	Qualitative research
	2021	Military settlements along the Ming Great Wall in Qinghai Province, China	Through field research and GIS analysis, this study elaborated on the functional types of military settlements and constructing a central–radial defense system with their spatial distribution.	Quantitative research

Source: Statistics by the author.

shows the representative literature on research related to military settlements and summarizes their research objects, methods, and limitations.

2.2. Linear Military Heritage Corridor

2.2.1. Development of the Heritage Corridor Theory

International research on linear cultural heritage has evolved from concepts such as “greenway”, “heritage corridor”, and “cultural routes” to “linear cultural heritage”. The concept of a heritage corridor originated in the United States in the 1980s, and its birth can be traced back to the evolution of the greenway concept [47]. Whyte, William H. (1959) first proposed the concept of “greenway” in his monograph [48]. Heritage corridors can be cultural landscapes such as historical transportation routes, war sites, or coastal areas. In the early 1990s, Little Charles E. (1990) and JG Fabos (1995) both believed that the types of greenways include cultural and historical greenways [49,50]. This type of greenway has rich historical heritage content, similar to the characteristics of a heritage corridor. In 1993, Flink, Charles A. et al. (1993) stated in their book Greenways: A Guide to Planning, Design, and Development that heritage corridors are different from green corridors in that they are a linear landscape that integrates rich and unique cultural resources [51]. Research on heritage corridors in China is currently lagging. The theory of heritage corridors first emerged in the early 21st century. Wang Zhifang and Sun Peng (2001) pointed out that the components of heritage corridors are system interpretation, heritage resources, paths, and vegetation corridors [52]. Yu Kongjian and Li Dihua (2003) elaborated on the definition and characteristics of heritage corridors, namely, heritage corridors are linear heritage areas that can contain a variety of different heritages, have scale flexibility, integrity, and comprehensiveness of heritage areas, and are of great significance to natural systems and the economy [53]. Li Wei et al. (2004) not only introduced the protection framework of the Grand Canal Heritage Corridor in China in detail [54] but also distinguished between linear cultural heritage such as “heritage corridors” and “cultural routes [55]. In recent years, linear heritage sites such as the Grand Canal [56], the Silk Road [57], the Three Gorges of the Yangtze River [58], the ancient Great Wall ruins [59], the Ancient Shu Road [60], and the Ancient Tea Horse Road [61] have received increasing attention. Research on China’s heritage corridors has developed rapidly, mainly focusing on canals, river canyons, roads, railways, etc. It not only emphasizes historical and cultural connotations but also emphasizes the protection of nature and the economy.

2.2.2. Current Status and Reference Significance of Military Heritage Corridor

Fieber K. D. et al. (2017) investigated used historical topographic maps, archeological records, LiDAR point cloud data, and other data from different periods. They also used 4D modeling, SfM photogrammetry, and multi-temporal LiDAR-GIS methods to look at how the landscape changed at three Roman fortress sites in England along Hadrian’s Wall over time, including how it changed due to natural erosion and other disasters [62]. Bachagha Nabil et al. (2020) used high-resolution remote sensing images and GIS to reconstruct a Roman military fortress system in southern Tunisia. The system consists of strategically located fortresses and towers that can effectively monitor and control the surrounding areas. This study provides new insights into the Roman Empire’s military defense system in arid areas [63]. Filzwieser, Roland et al. (2022) conducted a multidisciplinary study of the medieval castle of Dernberg in Austria and its surrounding abandoned villages. Using historical maps, aerial photography, laser scanning, and magnetic detection, they reconstructed the area’s defense system and historical landscape, revealing the development and evolution of the castle, village, surrounding agricultural land, and road network [64]. Although integrating different data sources can verify and complement each other, the uneven data quality and huge amount of information also require superior technology and more time investment, making extracting valuable information more complicated. Chinese researchers Fan Qingbin et al. (2022) used OSL and ¹⁴C dating to examine how oases became deserts from the Han Dynasty to the Ming and Qing Dynasties. They used the Suoyang City Ruins in the Hexi Corridor, which has some of China’s oldest city sites, as an example and found that people leaving the military settlements was linked to desertification [65]. Pydyn Andrzej and Popek Mateusz (2020) used radiocarbon dating and other methods to study the period of use and functional structure of the medieval bridge remains at Lake Lednica in Poland. The study reflected the defense and transportation needs of the early Piast dynasty and further revealed the important political and military status of the Lake Lednica region in the early Middle Ages [66]. Canadian scholar Bazely Susan Marie (2024) used the Rideau Canal and Kingston Fortifications World Heritage Site in Canada from a historical geography perspective to reveal the heritage site’s complexity and contradictions regarding geography, history, and cultural narrative (

Table 2. Relevancy of research in different research fields to this study.

Literature Source	Research Object	Research Field	GIS Research Methods	Relevancy
Fieber K. D. et al. (2017) [62]	Roman fort ruins along Hadrian’s Wall in England	Earth and environmental science	Four-dimensional modeling, drone surveys, SfM photogrammetry, and multi-temporal LiDAR-GIS	The author’s integrated analysis of multi-source data are significant to this study’s data sources and references, such as historical archive data, modern measurement data, and archeological data; this helps to more comprehensively understand the historical status of military cultural heritage.
Fan Qingbin et al. (2022) [65]	Jizhen military settlement of the Ming Great Wall	History, archaeology, and paleoecology	OSL and 14C dating	The conclusion of this study makes this study aware of the relationship between oases and military settlements. Environmental factors (especially oases and water systems) are heterogeneous characteristics of the Hexi Corridor compared with other military settlement areas.
Bazely Susan Marie (2024) [67]	Intangible cultural heritage along the Ming Great Wall	Historical geography	Kernel density estimation, standard deviation ellipse, and analytic hierarchy process	This situation is similar to the current situation faced by military settlements along the Ming Great Wall. Due to the difficulty in defining the protection scope of the Great Wall and the lack of awareness of cultural heritage protection, many military settlements along the Great Wall lack systematic research and protection [9]; this highlights the urgency and necessity of this study. The study of military settlements along the Ming Great Wall helps to enhance the unity of the two in cultural cognition and heritage protection.

Source: Statistics by the author.

). The study pointed out that significant geographical space, historical development, and cultural cognition differences have challenged their unity as a single World Heritage Site [67].

The growth of GIS (geographic information science) and related technologies has made studying heritage corridors along lines easier and helped improve analytical research (

Table 3. Application of GIS Methods in the study of linear military heritage corridors.

Literature Source	Research Object	GIS Research Methods	Pros	Cons
Volkmann Armin (2017) [68]	Main River Region on the border of the Roman Empire	Delaunay triangulation and Least Cost Path Analysis	It effectively captures the spatial correlation between the sites, fully considers the impact of terrain and obstacles on the transportation system, and evaluates the traffic accessibility between the sites.	The demand for data are high, and the model interpretation is relatively complex. The results of the analysis may need to be combined with historical information and other materials and data for comprehensive interpretation.
Wang Linfeng (2018) [11]	Jizhen military settlement of the Ming Great Wall	GIS terrain and buffer analysis	Terrain modeling can analyze the impact of terrain on settlement distribution in multiple dimensions; buffer analysis is simple and efficient, supports a variety of geographical elements, and has a wide range of applicability.	Although terrain analysis has made up for the defect of buffer analysis based only on geometric distance to a certain extent, a comprehensive analysis needs to include more influencing factors.
Lin Feiyang et al. (2022) [59]	Intangible cultural heritage along the Ming Great Wall	Kernel density estimation, standard deviation ellipse, and analytic hierarchy process	Kernel density and standard deviation ellipse have good visualization effects and apply to various data types. AHP can comprehensively consider multiple factors and scientifically calculate weights, avoiding subjective arbitrariness.	The combination of AHP and GIS methods increases the system’s complexity, and the data’s integrity will also affect the reliability of the decision-making results.
Shen Yang et al. (2020) [42]	Xiaohekou section of the Ming Great Wall	GIS terrain and elevation analysis	The analysis of terrain and elevation effectively quantifies the distribution pattern of military facilities on the Ming Great Wall, providing a basis for studying visual range and firearms range.	Terrain and elevation analysis can only reflect some aspects of the layout of the Ming Great Wall and its military defense facilities, and more influencing factors need to be included in the analysis in the future.
Yu Jie et al. (2023) [57]	Four categories of cultural heritage in the Chinese section of the Silk Road, including military defense sites	GIS visualization and historical material analysis	Combining GIS and historical materials provides visual analysis, improving accuracy and data integration.	The uneven quality of information and the huge amount of information may make it difficult to extract valuable information.

Source: Statistics by the author.

). GIS and remote sensing images efficiently provide spatial information about the study area. Volkmann Armin, a German scholar, conducted research in 2017 on the Main River Region on the border of the Roman Empire. He found that military settlement patterns, road networks, and fortifications changed over time and were spread out in different places. The author believes that the integration of diverse cultures has gradually deepened under the influence of the military and economy [68]. Chinese scholar Wang Linfeng (2018) established a specific relationship between the spatial characteristics of the Jizhen military settlement and the environment from the perspective of slope and water resources. The concept of the Great Wall military buffer zone is proposed to link the Great Wall protection zoning policy with the overall protection of heritage values [11]. From a macro perspective, Lin Feiyang et al. (2022) looked at the distribution pattern and resistance factors of intangible cultural heritage along the Ming Great Wall. They also talked about how the human–land relationship of the intangible cultural heritage space of the Ming Great Wall changed over time. They also said that the Great Wall and military fortresses in the Hexi Corridor region show much cultural diversity [59]. Shen Yang et al. (2020) used the military geomorphology theory to examine how the Great Wall, signal towers, and other features were chosen for their locations in the Xiaohekou section and their role in military operations [42]. In 2023, Yu Jie et al. studied the four main types of cultural heritage sites along the Chinese part of the Silk Road. These sites included military defense sites and were used as an example to look into the factors that affect how cultural ecosystems change over time. The authors believe the protection and sustainable use of cultural heritage sites must comprehensively consider cultural ecosystem services and environmental status [57].

GIS technology integrates historical maps, LiDAR point clouds, and other multi-source data to build a spatiotemporal model, systematically analyzes the spatial distribution and evolution of military heritage, and solves the problem of fragmented data in traditional research; its kernel density analysis and standard deviation ellipse quantification tools transform qualitative descriptions into visual agglomeration patterns (such as linear defense corridors) to accurately locate the core area of heritage protection. Combined with the superposition analysis of environmental factors such as topography and hydrology, GIS reveals the site selection logic of “relying on mountains to control dangers” and “building cities by water” and clarifies the adaptive relationship between the defense system and the natural environment. In addition, combining multidisciplinary methods such as the analytic hierarchy process (AHP) is conducive to breaking through the limitations of a single method and promoting the comprehensiveness of research methods and results. Ultimately, it provides scientific support for the protection and sustainable use of military heritage. However, the current application of GIS technology in this field still has limitations: research focuses on macro linear corridors and surface area analysis. Although this reveals the overall spatial pattern and historical evolution, it ignores the systematic study of small and medium-scale point elements (such as military settlements and enemy towers). Specifically, there is a lack of in-depth discussion on the internal spatial composition, functional organization of the settlements, and their dynamic structural relationship with the linear corridors, resulting in insufficient recognition of the “homogeneous heterogeneous” characteristics of the heritage corridors-neither the functional homology of the elements within the defense system is fully analyzed, nor is it difficult to quantify the morphological differences in individual settlements due to environmental adaptation.

2.3. Research Gaps

In general, the academic community has conducted extensive research on defensive settlements and their defense systems from the perspectives of geographical distribution, settlement structure, morphological pattern evolution, and defense mechanisms. The intervention of architecture, military geography, historical geography, archaeology, and research methods such as GIS and fractal geometry has made the research on military defensive settlements more in-depth. Nonetheless, contemporary research encounters issues related to regional constraints and scale fragmentation. First, most studies are concentrated in the coastal areas of Jiangsu and Zhejiang and the Beijing–Tianjin–Hebei region, and less attention is paid to military settlements in the arid and semi-arid regions of the northwest, resulting in a lack of in-depth understanding of military settlements and their defense mechanisms in places such as the Hexi Corridor. Most studies focus on the settlement defense system under the macro-distribution pattern or the defense function of residential houses under the micro-architectural layout. There is a lack of research on the spatial morphology of settlements at the meso scale, making it difficult to fully reveal the spatial organization logic of military settlements and the principles of defense system construction. This inadequate research has led to a vague understanding of the inherent connection and synergy between military settlements’ distribution, morphology, and function and a lack of systematic research and understanding of defense mechanisms.

This study combines quantitative analysis, such as GIS methods and space syntax, with qualitative research from the perspective of history and typology. This study constructs a multi-scale research methodology of “macro-distribution pattern–meso-spatial form–micro-functional organization”. The multi-scale collaborative defense mechanism of the military settlements in the Hexi Corridor is revealed from the perspective of a “distribution system–spatial organization system–functional element system”. On this basis, the basic unit composition of its spatial organization and the structural relationship between its prototypes are further explored, and the intrinsic correlation between spatial layout and military defense system is revealed. This way, the spatial layout characteristics of military settlements along the Ming Great Wall in the Hexi Corridor are comprehensively analyzed. The construction of this theoretical framework is conducive to deepening the systematic understanding of the spatial organization laws of linear military heritage; at the practical level, it is helpful to promote the transformation of linear cultural heritage research from “surface coverage” to “point–line–surface integration”.

3. Materials and Methods

3.1. Study Area: Hexi Corridor

The study area, the Hexi Corridor (Figure 1a), is located northwest of Gansu Province (Figure 1b). It is a narrow corridor running from northwest to southeast, totaling 1200 km. It is adjacent to the Heli Mountain–Longshou Mountain in the north and the Qilian Mountains in the south. The region’s northwest terminus of the Ming Great Wall and the nexus of the Silk Road have historically served various roles in military defense, cultural exchange, and ecological transition. The Hexi Corridor has been a battleground for military strategists since ancient times (Figure 1c). Since the establishment of the “Four Hexi Commanderies” in the Han Dynasty, a three-dimensional defense system of “Great Wall-Military Town-Beacon Tower” has been formed to resist the invasion of Mongolian nomadic forces from the south; it is also a major transportation route connecting the Central Plains and the Western Regions for commercial trade and religious communication. The diverse ecological environment of the mountain–oasis–desert provides regional characteristics for the construction and development of local settlements. As a coupling and interweaving zone with multiple landforms, wars, and cultures, the Hexi Corridor has significant cultural and military characteristics. The ancient ancestors of the Hexi region resisted foreign invasions, such as Mongolian nomadic settlements, through scientific planning and systematic collaboration, a symbol of the military strategic wisdom of the ancient Chinese nation. The establishment of military settlements reflects the spatial distribution and internal morphological characteristics of top–down construction guided by military strategy, and it has witnessed and carried the development and evolution of China’s military civilization for thousands of years.

Through historical data and documents, geographic information databases, and field research, this study obtained 173 settlement coordinates (

Table 4. Statistics of military settlements in the Hexi Corridor.

Precinct	Town City	Wei City	Suo City	Bao City	Pass City
Ganzhou Town	1	1	1	50	2
Zhuanglang Lu	/	2	/	17	/
Dajing Lu	/	/	/	4	1
Liangzhou Lu	/	4	1	48	1
Suzhou Lu	/	1	1	36	2
Sum	173

Source: Statistics and plotting by the author.

) through statistics and processing with ArcGIS 10.8 and Excel. Detailed information is shown in

Table A1. Statistics and existing status of military settlements in the Hexi Corridor.

ID	Name	Sources	Latitude	Longitude	Level	Attribution	Remains	Status Assessment
1	Ganzhou	H-G-F	38.930904	100.456481	Town City	/	●	★★★★★
2	Shandan	H-G-F	38.78172	101.086879	Wei City	Town City	●	★★★★★
3	Gaotai	H-G-F	39.376395	99.816259	Suo City	Town City	●	★★★★★
4	Baba	H-G	39.48773861	99.70480621	Bao City	Town City	×	/
5	Banqiao	H-G	39.300732	100.256554	Bao City	Town City	×	/
6	Chuaizhuang	H-G	38.64314318	101.2728739	Bao City	Town City	●	★★
7	Ciergou	H-G	39.16353159	100.6209552	Bao City	Town City	×	/
8	Damaying City	H-G-F	38.340897	101.18968	Bao City	Town City	●	★★
9	Daman	H-G	38.78561355	100.4128381	Bao City	Town City	×	/
10	Dapankou	H-G	39.21042869	100.7868988	Bao City	Town City	×	/
11	Daqiaozhai	H-G	38.832713	100.83879	Bao City	Town City	×	/
12	Dongle	H-G-F	38.824175	100.8257	Bao City	Town City	●	★★★★★
13	Fengcheng	H-G	38.544265	101.378336	Bao City	Town City	×	/
14	Fuchang	H-G	38.620802	101.257424	Bao City	Town City	×	/
15	Ganjun	H-G	38.97902533	100.1865387	Bao City	Town City	×	/
16	Gucheng	H-G-F	38.54911407	100.4942485	Bao City	Town City	●	★★★
17	Guzhai	H-G	39.24526209	100.0598441	Bao City	Town City	×	/
18	Heicheng	H-G	38.37787935	101.0466112	Bao City	Town City	×	/
19	Heiquan	H-G-F	39.531491	99.625079	Bao City	Town City	●	★★
20	Hongquan	H-G	39.07761544	100.7384089	Bao City	Town City	●	★★
21	Hongshawo	H-G	39.03488249	100.5684641	Bao City	Town City	●	★★
22	Hongshui	H-G-F	38.43700422	100.8155694	Bao City	Town City	●	★★★★★
23	Huazhai	H-G-F	38.46702147	101.1503071	Bao City	Town City	●	★★★
24	Jingan	H-G	39.11280602	100.4166001	Bao City	Town City	×	/
25	Jiuba	H-G	39.5052588	99.68261361	Bao City	Town City	●	★★
26	Judi	H-G	38.82415078	100.4633824	Bao City	Town City	×	/
27	Liushu	H-G	39.319181	100.202571	Bao City	Town City	×	/
28	Liuba	H-G-F	39.39441	99.843005	Bao City	Town City	●	★★★★
29	Mingsha	H-G	39.17449415	100.3510523	Bao City	Town City	×	/
30	Nuanquan (1)	H-G	38.55275253	101.1339341	Bao City	Town City	×	/
31	Nuanquan (2)	H-G	39.14336559	99.58449217	Bao City	Town City	×	/
32	Pingchuan	H-G-F	39.335061	100.096017	Bao City	Town City	●	★★★
33	Pinglu	H-G	39.23756062	100.320015	Bao City	Town City	×	/
34	Qiba	H-G	39.431943	99.764326	Bao City	Town City	×	/
35	Qukou	H-G	39.35421468	99.90080841	Bao City	Town City	×	/
36	Shajing	H-G	39.09050615	100.2762431	Bao City	Town City	●	★★
37	Shixiakou	H-G-F	38.508792	101.419205	Bao City	Town City	●	★★★★★
38	Shunde	H-G	39.22019617	99.48259559	Bao City	Town City	×	/
39	Suihua	H-G	38.4690681	100.6891331	Bao City	Town City	×	/
40	Taiping	H-G	38.936385	100.612663	Bao City	Town City	×	/
41	Wayao	H-G	39.06363	100.443333	Bao City	Town City	×	/
42	Xidong	H-G	38.86293069	100.2345538	Bao City	Town City	×	/
43	Xiatianle	H-G	38.53888092	100.7373426	Bao City	Town City	×	/
44	Xiaoman	H-G	38.83382306	100.3810016	Bao City	Town City	×	/
45	Xinhe	H-G-F	38.64772975	101.2659109	Bao City	Town City	●	★★
46	Xinkaiba	H-G	38.59154734	101.0479201	Bao City	Town City	×	/
47	Xintian	H-G	38.56162126	100.583618	Bao City	Town City	×	/
48	Yangjiaba	H-G-F	38.4986307	101.1055414	Bao City	Town City	●	★★★
49	Yongxing	H-G	38.72013932	101.1548623	Bao City	Town City	×	/
50	Zhenxi	H-G	39.41346946	99.71354079	Bao City	Town City	×	/
51	Zhenyanba	H-G	39.34793915	99.76090116	Bao City	Town City	×	/
52	Ziniquan (1)	H-G	39.09358934	100.5346039	Bao City	Town City	●	★★
53	Ziniquan (2)	H-G	39.09710437	100.5382785	Bao City	Town City	●	★★
54	Hongsishan	H-G	38.88537347	101.0920742	Pass City	Town City	×	/
55	Shannan	H-G	39.09370065	100.5348963	Pass City	Town City	×	/
56	Liangzhou	H-G-F	37.923824	102.63502	Wei City	Liangzhou Lu	●	★★★★★
57	Zhenfan	H-G-F	38.623221	103.092106	Wei City	Liangzhou Lu	●	★★★★★
58	Yongchang	H-G-F	38.246854	101.969866	Wei City	Liangzhou Lu	●	★★★★★
59	Anyuanzhan	H-G	37.25798607	102.8556562	Wei City	Liangzhou Lu	●	★★
60	Gulang	H-G	37.465634	102.892767	Suo City	Liangzhou Lu	×	/
61	Heisonglin	H-G	37.353786	102.910144	Bao City	Liangzhou Lu	×	/
62	Gaomiaoer	H-G	37.662104	102.918197	Bao City	Liangzhou Lu	×	/
63	Sishui	H-G-F	37.587846	102.942034	Bao City	Liangzhou Lu	●	★★★
64	Yuandun	H-G	37.662281	102.956743	Bao City	Liangzhou Lu	●	★★
65	Yongfeng	H-G-F	37.669271	103.034474	Bao City	Liangzhou Lu	●	★★★
66	Zhangyi	H-G-F	37.521658	102.659834	Bao City	Liangzhou Lu	●	★★★
67	Shuangta	H-G-F	37.577628	102.876062	Bao City	Liangzhou Lu	●	★★
68	Jingbian	H-G	37.71113	102.939226	Bao City	Liangzhou Lu	×	/
69	Dahe	H-G-F	37.84889	102.737981	Bao City	Liangzhou Lu	●	★★
70	Sancha	H-G-F	38.148845	102.69187	Bao City	Liangzhou Lu	●	★★
71	Caiqi	H-G	38.224484	102.75401	Bao City	Liangzhou Lu	×	/
72	Zhenjing	H-G-F	38.215243	102.061964	Bao City	Liangzhou Lu	●	★★★
73	Shuimochuan	H-G	38.268885	101.732864	Bao City	Liangzhou Lu	×	/
74	Shuiquaner	H-G	38.37147	101.641825	Bao City	Liangzhou Lu	●	★★
75	Yongning	H-G	38.214228	102.61087	Bao City	Liangzhou Lu	×	/
76	Ningyuan	H-G-F	38.441604	102.184228	Bao City	Liangzhou Lu	●	★★★
77	Muyangchuanhedong	H-G	38.358691	102.098156	Bao City	Liangzhou Lu	×	/
78	Muyangchuanhexi	H-G	38.371178	102.068678	Bao City	Liangzhou Lu	×	/
79	Xincheng	H-G	38.199	101.58929	Bao City	Liangzhou Lu	×	/
80	Dingqiang	H-G	38.439976	101.514305	Bao City	Liangzhou Lu	●	★★
81	Gaogucheng	H-G	38.24757724	101.4604853	Bao City	Liangzhou Lu	×	/
82	Baba(1)	H-G	38.17380635	102.1011968	Bao City	Liangzhou Lu	×	/
83	Fenglepu	H-G	38.10424576	102.0973143	Bao City	Liangzhou Lu	×	/
84	Tanshankou	H-G	38.07803921	102.2545536	Bao City	Liangzhou Lu	×	/
85	Changning	H-G	38.61769997	102.4803829	Bao City	Liangzhou Lu	×	/
86	Yongchang	H-G	38.06542124	102.580356	Bao City	Liangzhou Lu	×	/
87	Shuangcheng	H-G	38.16636498	102.5842385	Bao City	Liangzhou Lu	×	/
88	Beigucheng	H-G	38.3002199	101.6872458	Bao City	Liangzhou Lu	×	/
89	Hongmiaoer	H-G	38.31645351	101.7386523	Bao City	Liangzhou Lu	×	/
90	Jinchuan	H-G	38.34796876	101.6798993	Bao City	Liangzhou Lu	×	/
91	Hedongpu	H-G	37.76436803	102.7725433	Bao City	Liangzhou Lu	×	/
92	Fenglepuzhai	H-G	38.06579211	102.3492669	Bao City	Liangzhou Lu	×	/
93	Changlongpu	H-G	38.04655227	102.4101931	Bao City	Liangzhou Lu	×	/
94	Fengyuan	H-G	38.13794149	102.2931507	Bao City	Liangzhou Lu	×	/
95	Shanggucheng	H-G	37.70491159	102.6026582	Bao City	Liangzhou Lu	×	/
96	Jiuduntan	H-G	38.14575166	102.7904865	Bao City	Liangzhou Lu	●	★★
97	Heishan	H-G	38.42263341	102.8911471	Bao City	Liangzhou Lu	●	★★
98	Siba	H-G-F	38.63048449	103.1551355	Bao City	Liangzhou Lu	●	★★
99	Hongsha	H-G-F	38.67577493	103.1820327	Bao City	Liangzhou Lu	●	★★
100	Shashan	H-G	38.58036071	102.9911345	Bao City	Liangzhou Lu	●	★★
101	Qingsong	H-G	38.52508307	102.9799819	Bao City	Liangzhou Lu	●	★★
102	Hongya	H-G	38.38214278	102.8320634	Bao City	Liangzhou Lu	×	/
103	Maopuci	H-G	38.32728254	101.9117267	Bao City	Liangzhou Lu	×	/
104	Toudunying	H-G	37.83075125	102.9934494	Bao City	Liangzhou Lu	●	★★
105	Gaogou	H-G-F	37.91285155	102.8749782	Bao City	Liangzhou Lu	●	★★
106	Tuanzhuangyinger City	H-G	38.08566002	102.7994499	Bao City	Liangzhou Lu	●	★★
107	Minqin Ancient City	H-G	38.85491589	103.2148527	Bao City	Liangzhou Lu	●	★★
108	Shuangjing (1)	H-G-F	37.30523586	103.6836943	Bao City	Liangzhou Lu	●	★★
109	Gulang Xinguan	H-G	37.392257	102.92932	Pass City	Liangzhou Lu	×	/
110	Zhuanglang	H-G-F	36.738702	103.261221	Wei City	Zhuanglang Lu	●	★★★★★
111	Heigucheng	H-G	37.242994	102.589328	Wei City	Zhuanglang Lu	●	★★
112	Shajinger	H-G-F	36.147497	103.628366	Bao City	Zhuanglang Lu	●	★★★
113	Kushuiwan	H-G	36.250988	103.428327	Bao City	Zhuanglang Lu	●	★★★★
114	Yehucheng	H-G-F	36.371099	103.398412	Bao City	Zhuanglang Lu	●	★★★★
115	Hongchengzi	H-G-F	36.461156	103.391106	Bao City	Zhuanglang Lu	●	★★★★★
116	Qingsier	H-G-F	36.532726	103.380027	Bao City	Zhuanglang Lu	●	★★★★
117	Nandatongshankou	H-G	36.616609	103.347304	Bao City	Zhuanglang Lu	●	★★★★
118	Daliushu	H-G	36.673852	103.298596	Bao City	Zhuanglang Lu	●	★★★
119	Heichengzi	H-G-F	36.653815	103.315462	Bao City	Zhuanglang Lu	●	★★★
120	Machanggou	H-G	36.800821	103.210643	Bao City	Zhuanglang Lu	×	/
121	Wusheng	H-G	36.882303	103.166033	Bao City	Zhuanglang Lu	●	★★★★
122	Chakou	H-G-F	37.024229	103.082025	Bao City	Zhuanglang Lu	●	★★
123	Zhenqiang	H-G	37.14284	102.888293	Bao City	Zhuanglang Lu	×	/
124	Nandatong River	H-G-F	36.54203725	102.9195476	Bao City	Zhuanglang Lu	×	/
125	Songshan	H-G	37.1143806	103.491565	Bao City	Zhuanglang Lu	●	★★
126	Tongyuan	H-G-F	36.69245303	103.0603623	Bao City	Zhuanglang Lu	●	★★
127	Xidatong	H-G-F	36.52328074	102.8793293	Bao City	Zhuanglang Lu	●	★★★
128	Pingcheng	H-G-F	36.96468651	103.3522296	Bao City	Zhuanglang Lu	●	★★
129	Tumen	H-G-F	37.614347	103.070705	Bao City	Dajing Lu	●	★★★
130	Dajingying	H-G-F	37.475389	103.410774	Bao City	Dajing Lu	●	★★★★
131	Peijiaying	H-G-F	37.473346	103.521733	Bao City	Dajing Lu	●	★★★
132	Aba	H-G-F	37.469585	103.679123	Bao City	Dajing Lu	●	★★★
133	Shixia	H-G	37.575205	103.467204	Pass City	Dajing Lu	×	/
134	Suzhou	H-G-F	39.743729	98.509815	Wei City	Suzhou Lu	●	★★★★★
135	Zhenyi	H-G-F	39.792026	99.472747	Suo City	Suzhou Lu	●	★★★★★
136	Linshuizhan	H-G	39.772914	98.779473	Bao City	Suzhou Lu	×	/
137	Heqing	H-G	39.553777	98.974104	Bao City	Suzhou Lu	×	/
138	Xinchenger	H-G-F	39.884027	98.448596	Bao City	Suzhou Lu	●	★★★
139	Xiagucheng	H-G	39.813355	98.792004	Bao City	Suzhou Lu	×	/
140	Huangcaoba	H-G	39.267077	99.07336	Bao City	Suzhou Lu	×	/
141	Jinfosi	H-G	39.419193	98.773834	Bao City	Suzhou Lu	×	/
142	Qingshui	H-G-F	39.360804	99.042781	Bao City	Suzhou Lu	●	★★★
143	Shuangjing (2)	H-G	39.758285	99.066214	Bao City	Suzhou Lu	●	★★
144	Jintasi	H-G	39.652383	98.346231	Bao City	Suzhou Lu	×	/
145	Liangshankou	H-G	39.832901	98.639414	Bao City	Suzhou Lu	×	/
146	Shiyingzhuang	H-G	39.951216	98.368763	Bao City	Suzhou Lu	●	★★
147	Yemawan	H-G	39.913965	98.392659	Bao City	Suzhou Lu	●	★★
148	Maolaiquan	H-G	39.562773	98.199679	Bao City	Suzhou Lu	●	★★
149	Shiguaner	H-G	39.85011	98.175748	Bao City	Suzhou Lu	×	/
150	Shengou	H-G	39.679584	99.573824	Bao City	Suzhou Lu	×	/
151	Shawan	H-G	39.675711	99.597516	Bao City	Suzhou Lu	×	/
152	Linhe	H-G	39.625819	99.609866	Bao City	Suzhou Lu	×	/
153	Yanchi	H-G	39.73344	99.272613	Bao City	Suzhou Lu	×	/
154	Yanzhi	H-G	39.601131	99.652767	Bao City	Suzhou Lu	×	/
155	Hongsi	H-G	39.39814309	98.87646999	Bao City	Suzhou Lu	×	/
156	Xidianzi	H-G	39.66910411	98.7049148	Bao City	Suzhou Lu	×	/
157	Shahe	H-G	39.69074892	98.58065753	Bao City	Suzhou Lu	×	/
158	Hongshan	H-G	39.48712733	98.72014633	Bao City	Suzhou Lu	×	/
159	Yanchizong	H-G	39.4089655	99.17588993	Bao City	Suzhou Lu	×	/
160	Maying	H-G	39.33428513	99.23568706	Bao City	Suzhou Lu	×	/
161	Zhongzhai	H-G	39.36284426	99.13287419	Bao City	Suzhou Lu	×	/
162	Hexi	H-G	39.72312353	99.55498148	Bao City	Suzhou Lu	×	/
163	Yingpanzi	H-G	39.78516072	98.99421126	Bao City	Suzhou Lu	●	★★
164	Xiaojianiuzhuangzi (1)	H-G	39.83327955	98.97173971	Bao City	Suzhou Lu	●	★★
165	Xiaojianiuzhuangzi (2)	H-G	39.84618734	98.92664018	Bao City	Suzhou Lu	●	★★
166	Xiaojianiuzhuangzi (4)	H-G	39.85648387	98.90963926	Bao City	Suzhou Lu	●	★★
167	Xiaojianiuzhuangzi (3)	H-G	39.85122173	98.92055169	Bao City	Suzhou Lu	●	★★
168	Yuanyangchi	H-G	39.85350731	98.8955707	Bao City	Suzhou Lu	●	★★
169	yangjiajing	H-G	39.82862458	98.9883245	Bao City	Suzhou Lu	●	★★
170	Shuangchengzi	H-G	40.42443171	99.67759729	Bao City	Suzhou Lu	×	/
171	Shazhou	H-G-F	40.14088623	94.66384934	Bao City	Suzhou Lu	●	★★★★★
172	Jiayuguan	H-G-F	39.801552	98.216055	Pass City	Suzhou Lu	●	★★★★
173	Yumen	H-G	40.35356373	93.86406541	Pass City	Suzhou Lu	●	★★

Source: statistics and plotting by the author. ● indicates that the ruins of settlement buildings still exist, on the contrary, × indicates that they do not exist. The symbol ★ in the table indicates that it has completely disappeared; ★★ indicates that only ruins remain; ★★★ indicates that it is only visible in historical satellite images; ★★★★ indicates that the spatial texture of the settlement is maintained; and ★★★★★ indicates that the spatial texture of the settlement is well preserved. The selection criteria for the 173 military settlements in this study are coded in the Source column: H: Historical data and documentary records; G: geographic information database; F: field verification.

. Among them, 85 are existing settlements (including ruins) (

Table A2. Statistics and existing status of military settlements in the Hexi Corridor.

ID	Name	Length (m)	Width (m)	Perimeter (m)	Area (km2)	Aspect Ratio	Shape Index
1	Ganzhou	2140.50	1836.06	7601.42	3515.92	1.17	1.13
2	Liangzhou	2326.83	1345.98	7182.57	2724.73	1.73	1.11
3	Suzhou	2255.64	1005.54	6324.27	1749.66	2.24	1.09
4	Yongchang	1240.54	1045.80	4519.53	1264.81	1.19	1.13
5	Shandan	1214.04	1039.17	4464.95	1239.78	1.17	1.13
6	Shazhou	1204.51	947.78	4066.35	931.97	1.27	1.12
7	Zhenfan	1021.54	920.65	3776.11	862.17	1.11	1.13
8	Zhuanglang	1205.68	641.19	3515.58	663.81	1.88	1.10
9	Gaotai	958.11	764.75	3156.56	595.99	1.25	1.12
10	Hongshui	738.84	695.77	2776.99	457.06	1.06	1.13
11	Zhenyi	663.75	600.71	2430.88	368.07	1.10	1.13
12	Pingcheng	668.15	605.52	2246.59	342.88	1.10	1.13
13	Dajing	667.32	499.00	2219.63	310.12	1.34	1.12
14	Pingchuan	531.98	343.40	1734.60	132.96	1.55	1.12
15	Shuiquan	691.00	213.05	1660.39	122.18	3.24	1.05
16	Dongle	571.70	247.29	1601.25	129.18	2.31	1.08
17	Shixiakou	510.90	223.37	1431.59	108.97	2.29	1.09
18	Aba	409.83	293.30	1382.68	116.61	1.40	1.12
19	Hongchengzi	434.69	297.19	1370.71	118.22	1.46	1.12
20	Songshan	341.63	338.54	1359.15	103.40	1.01	1.13
21	Qingshui	403.54	347.95	1353.36	119.43	1.16	1.13
22	Zhenjing	413.86	326.01	1342.61	110.05	1.27	1.12
23	Huazhai	380.50	303.10	1323.36	96.07	1.26	1.12
24	Liuba	351.71	325.16	1292.53	104.20	1.08	1.13
25	Nandatonghe	388.50	263.87	1288.37	100.05	1.47	1.12
26	Sishui	377.26	300.71	1279.91	105.06	1.25	1.12
27	Yongfeng	360.57	296.64	1277.76	101.06	1.22	1.13
28	Gucheng	334.36	311.61	1271.42	85.53	1.07	1.13
29	Tumen	353.91	315.38	1255.88	97.59	1.12	1.13
30	Xidatong	425.91	218.35	1244.20	86.39	1.95	1.10
31	Peijiaying	352.21	294.11	1233.28	91.28	1.20	1.13
32	Dahe	460.99	180.87	1225.26	76.34	2.55	1.07
33	Heiquan	349.18	279.08	1219.57	91.88	1.25	1.12
34	Ningyuan	391.84	239.83	1217.46	82.34	1.63	1.11
35	Shuangta	320.34	291.56	1171.58	86.01	1.10	1.13
36	Shuangjing (1)	318.47	275.32	1157.34	68.91	1.16	1.13
37	Siba	281.03	276.16	1086.27	74.97	1.02	1.13
38	Damaying City	315.43	251.02	1045.46	67.67	1.26	1.12
39	Kushuiwan	269.48	259.33	1027.85	65.95	1.04	1.13
40	Wusheng	289.58	210.13	991.14	59.85	1.38	1.12
41	Zhangyi	322.42	186.51	953.90	47.99	1.73	1.11
42	Shajing	319.69	187.54	952.42	52.21	1.70	1.11
43	Shajinger	254.70	216.79	925.88	53.46	1.17	1.13
44	Jiayuguan	275.60	194.19	905.86	40.06	1.42	1.12
45	Chakou	295.12	169.80	869.26	45.03	1.74	1.11
46	Yehucheng	233.03	160.71	778.22	36.61	1.45	1.12
47	Tongyuan	231.53	134.57	726.36	29.29	1.72	1.11
48	Hongsha	216.66	154.39	714.02	31.56	1.40	1.12
49	Yangjiaba	187.30	152.96	689.53	27.24	1.22	1.13
50	Heishan	237.43	166.09	689.26	28.16	1.43	1.12
51	Yingpanzi	183.85	162.93	688.87	27.19	1.13	1.13
52	Maolaiquan	174.32	161.81	650.65	24.78	1.08	1.13
53	Gaogou	152.49	141.75	619.02	18.56	1.08	1.13
54	Shuangjing (2)	178.67	153.48	618.22	23.66	1.16	1.13
55	Anyuanzhan	186.85	124.89	584.65	20.31	1.50	1.12
56	Qingsong	144.35	125.57	559.54	12.88	1.15	1.13
57	Qingsier	164.16	142.13	559.26	19.28	1.16	1.13
58	Qingchenger	151.47	135.19	546.19	18.59	1.12	1.13
59	Dingqiang	159.23	135.01	545.49	17.77	1.18	1.13
60	Tuanzhuangying	145.70	121.47	529.55	15.77	1.20	1.13
61	Jiuba	137.05	124.52	517.87	13.76	1.10	1.13
62	Toudunying	136.11	117.23	497.74	14.11	1.16	1.13
63	Sancha	127.38	121.80	481.85	14.49	1.05	1.13
64	Minqin ancient city	130.63	116.42	464.27	12.51	1.12	1.13
65	Yemawan	116.88	114.01	453.35	12.91	1.03	1.13
66	Daliushu	98.24	93.64	378.89	8.97	1.05	1.13
67	Heichengzi	107.85	91.61	378.46	8.90	1.18	1.13
68	Hongshawo	109.19	72.89	354.61	7.34	1.50	1.12
69	Shiyingzhuang	90.35	83.32	345.27	7.45	1.08	1.13
70	Yangjiajing	96.95	70.16	314.26	6.23	1.38	1.12
71	Xiaojianiuzhuangzi (1)	109.63	59.67	311.95	5.69	1.84	1.10
72	Yuanyangchi	90.20	81.70	296.67	6.38	1.10	1.13
73	Heigucheng	93.09	70.41	292.81	5.18	1.32	1.12
74	Shashan	94.83	67.62	291.30	5.12	1.40	1.12
75	Chuaizhuang	82.81	65.55	285.92	5.05	1.26	1.12
76	Hongquan	82.18	61.02	275.03	4.64	1.35	1.12
77	Xiaojianiuzhuangzi (3)	63.17	50.91	211.72	2.94	1.24	1.13
78	Xiaojianiuzhuangzi (2)	66.83	50.70	203.70	2.79	1.32	1.12
79	Xiaojianiuzhuangzi (4)	63.47	51.30	203.50	2.72	1.24	1.13
80	Xinhe	53.69	44.00	188.43	2.20	1.22	1.13
81	Yuandun	55.69	40.64	182.13	2.02	1.37	1.12
82	Jiuduntan	44.42	33.21	145.61	1.32	1.34	1.12
83	Yumen	26.88	26.68	105.09	0.69	1.01	1.13
84	Ziniquan (2)	28.62	21.64	98.77	0.60	1.32	1.12
85	Ziniquan (1)	28.08	15.94	84.41	0.41	1.76	1.11

Source: Statistics and plotting by the author.

). The spatial configurations of Wei City and Suo City’s higher-level cities are well-preserved. The Ming and Qing Dynasties built most of their internal road network skeletons, which remain intact and continue to evolve today. We can better plan their defenses and camps along the Ming Great Wall by looking at how military settlements are spread out and organized in the Hexi Corridor; this helps protect and grow the military settlements along the Wall and pass on the cultural heritage of the Great Wall.

3.2. Research Methods

The study of military settlements in the Hexi Corridor was carried out using the following three aspects: spatial distribution pattern, distribution influencing factors, and settlement spatial morphology (Figure 2). First, the average nearest neighbor and kernel density were used to examine how military settlements are grouped in space. The Global Moran and local LISA indexes were then used to explain how military settlements in the same country are linked in space. Second, regarding distribution-influencing factors, this study used GIS to analyze military settlements’ distribution elevation range and buffer zone establishment to analyze the spatial correlation between water systems, oases, the Great Wall, and military settlements. Finally, this study examined military settlements’ scale and boundary morphology using morphological indexes and GIS spatial statistics. Using space syntax, it also looked at military settlements’ internal spatial morphology and functional facility distribution. Keyhole satellite maps were also included in this study. Through the above analysis, this study tries to explain how the military defense system and the culture of military camps are reflected in how settlements are built.

3.2.1. Average Nearest Neighbor Index

From the overall distribution of the Hexi Corridor, military settlements can be abstracted into point elements and presented as coordinate points. Based on the ratio of the average nearest neighbor distance (Observed Mean Distance) to the theoretical nearest neighbor distance (Expected Mean Distance) between each point element in the region, the average nearest neighbor index can determine the type of spatial distribution and agglomeration degree of the points. Reference [69] provides the formula.

3.2.2. Kernel Density Estimation

Kernel density estimation is a non-parametric method for estimating the distribution density of point features. The calculation formula is shown in [70]. Kernel density estimation can better observe the spatial aggregation characteristics and degree of settlement in a region. The distribution of settlements in the region can be obtained by analyzing the kernel density index of military settlement coordinate points.

3.2.3. Spatial Autocorrelation Analysis

The Global Moran’s I index reflects the similarity of the attribute values of spatially adjacent or spatially neighboring regional units [71]. It can evaluate the agglomeration of military settlements in the Hexi region. The Local Indications of Spatial Association (LISA) measures how spatially agglomerated the regional unit is compared to the regional units around it, with similar values [72]. It can further examine the correlation between the distribution density of military settlements on a county scale. The formula for the calculation appears in [73].

3.2.4. Buffer Analysis

Some scholars have found that, no matter what geographical environment a settlement is in, 3 km is the average distance that can be easily covered by walking daily [74]. At the same time, this study refers to the buffer zone settings for the spatial distribution of traditional villages in Gansu Province provided by Xue Chenhao and Wang Shengpeng (2024) [75]. This study conducted sensitivity tests on the buffer zone in different data intervals based on the water system, the Ming Great Wall (linear elements), and the oasis (surface elements) of the Hexi Corridor. The results show that the 3 km, 6 km, and 12 km buffer zones can effectively cover the spatial coupling characteristics of the settlements and environmental elements in the Hexi Corridor (

Table 5. Literature support for buffer zone setting.

Influencing Factors	Value Classification	Classification Basis
Terrain	1000–1440 m	The average difference between the highest and lowest settlements’ altitudes
	1441–1880 m
	1881–2320 m
	2321–2760 m
	2761–3200 m
Water System	0–1 km	Xue Chenhao and Wang Shengpeng (2024) [75]
	1–3 km
	3–6 km
	6–12 km
	Over 12 km
Oasis	Inside the oasis	Yiannakou Athena et al. (2017) [74]
	0–1 km
	1–3 km
	3–6 km
	6–12 km
	Over 12 km
The Great Wall of Ming Dynasty	0–3 km	Yiannakou Athena et al. (2017) [74]
	3–6 km
	6–12 km
	12–24 km
	Over 24 km

Source: Statistics and plotting by the author.

). In addition, the additional setting of the 0–1 km buffer zone is intended to further analyze the relationship between military settlements and environmental elements. In addition, the additional setting of the 0–1 km buffer zone is intended to further analyze the relationship between military settlements and environmental elements. By putting military settlement point data on top of buffer layers of elevation, water systems, the Great Wall, and oasis in the area, this study looks at how environmental factors affect the pattern of military settlements.

3.2.5. Shape Index

The shape index is a mathematical index widely used in landscape ecology. Settlement morphology results from the continuous evolution of space under the influence of self-organization and other organizations. In this study, this indicator mainly characterizes the regularity of settlement morphology. This study uses the settlement morphology index and conducts a characteristic analysis of military settlements in the Hexi region. The settlement morphology index calculation formula is

$$S={\displaystyle \frac{P}{1.5\lambda -\sqrt{\lambda }+1.5}}\sqrt{{\displaystyle \frac{\lambda }{A\pi }}}$$

(1)

where $P$ is the perimeter of the external boundary of the settlement, $A$ is the area of the settlement, and $\lambda$ is the aspect ratio of the settlement plane. When $S<2$: $\lambda <1.5$, it is a clustered settlement; $1.5\le \lambda <2$, it is a clustered settlement with a strip tendency; $\lambda \ge 2$, it is a strip settlement.

3.2.6. Spatial Syntax

Space syntax is a theory that takes spatial organization as its core and reveals the relationship between space itself and between space and society by quantifying the relationship between the local and the whole in space [76]. The degree of aggregation within military settlement space can be determined through integration, illustrating the connectivity and accessibility between unit spaces within the system. The unit space with a larger integration value has greater convenience and a higher degree of aggregation, and vice versa. Intelligibility analysis refers to the functional correlation analysis of connectivity value and global integration. In the analysis of military settlement space morphology, it can be used to evaluate the recognizability of settlement space. The higher the intelligibility value, the easier people can understand the overall spatial characteristics based on their local spatial perception. The detailed formula of space syntax analysis can be found in [77].

3.3. Data Sources

The main data sources include:

(1) Settlement distribution data. Most of the information about where military bases were and how they were arranged in the Hexi region comes from the Gansu General History (甘肃通志), the Gansu Prefecture and county annals (甘肃府县志辑), the Collation and annotation of the complete records of Wuliang (五凉全志校注), the Yongchang County annals during the Jiaqing period (嘉庆永昌县志), the Local chronicles of Wuwei (武威地方志), the Ganzhou Prefecture annals (甘州府志), the Zhangye City annals (张掖市志), the Minqin county annals (民勤县志), the Zhenfan county annals (镇番县志), the Records of Tiancheng Village (天城村志), the Zhuanglang County annals (庄浪县志), the Shandan County annals (山丹县志), the Records of Su Town (肃镇志) and the Gaotai County annals (高台县志) located in the Gansu Local History Network (https://www.gsdfszw.org.cn/, accessed on 14 December 2024). The book also includes local chronicles such as Dunhuang City annals (敦煌市志) and other local chronicles. It is supplemented with relevant books and documents, such as Chronicles of The Great Wall of China. The Wall In Maps and Pictures (中国长城志·图志) and Bian Zheng Kao (边政考) as references.

(2) Settlement spatial data. DEM elevation data, administrative division data, Great Wall and military settlement coordinate points, historical satellite image data, and Hexi Corridor Oasis data are the different spatial data types (

Table 6. Source of military settlement spatial data.

No.	Data Types	Source
1	DEM elevation data	Copernicus DEM, COP-DEM, with a resolution of 30 m (https://panda.copernicus.eu/panda, accessed on 14 December 2024).
2	Administrative division data	National Basic Geographic Information Center (http://www.ngcc.cn/, accessed on 21 December 2024); Geospatial Data Cloud (https://www.gscloud.cn/, accessed on 17 November 2024).
3	Coordinate points of the Great Wall and military settlements	Harvard World Map (https://worldmap.maps.arcgis.com/, accessed on 21 November 2024); China Great Wall Heritage Network (http://www.greatwallheritage.cn/CCMCMS/, accessed on 29 December 2024); Great Wall Station (http://www.thegreatwall.com.cn/public/gwdb/, accessed on 24 December 2024); THE HISTORICAL ATLAS OF CHINA (Volume VII).
4	Historical satellite image data	Keyhole satellite images from the United States (USGS) Geological Survey in the 1960s and 1970s (https://earthexplorer.usgs.gov/, accessed on 14 December 2024); Google Earth high-resolution satellite imagery (https://google.cn/intl/zh-CN/earth/, accessed on 14 December 2024).
5	Oasis data of the Hexi Corridor in 1986 [78]	Xie, Y., Zhang, X., Liu, Y., Huang, X., Li, R., Zong, L., Xiao, M., Qin, M. (2022). Oasis dataset of Hexi Corridor based on Landsat data (1986–2020). National Tibetan Plateau/Third Pole Environment Data Center.

Source: Statistics and plotting by the author.

). Among them, the information on 173 military settlements is based on historical and documentary records in the above-mentioned local chronicles. The authors determined the location and current status of the settlements through multiple open geographic information databases, such as the Great Wall Station, and visited and investigated some of the settlements.

(3) Settlement spatial morphology data. Because different historical documents show the same military settlement in different ways, this study took historical documents, settlement maps, and satellite images from different periods and put them all together. We then chose 18 military settlements with relatively well-preserved spatial morphology as the research objects (Figure 3, Figure 4 and Figure 5). The axis map was drawn using AutoCAD (2018 version), and the spatial syntax axis model was analyzed using Depth Map (beta 1.0 version). The remaining samples were analyzed quantitatively using ArcGIS (10.8 version) regarding settlement size and shape; this was performed so that more research could be carried out on the location and shape of military settlements in the Hexi region.

(4) Field investigation and settlement verification data. In order to gain a deeper understanding of the spatial layout of military settlements in the Hexi Corridor, the research team visited 51 local military settlements by comparing satellite image data with historical documents. The team conducted targeted visits and surveys of the settlements’ residential houses, streets, and public spaces. This study selected 18 typical military settlements with relatively well-preserved spatial forms. The settlement level, different jurisdictions, morphological characteristics, preservation status, and data completeness criteria are the basis for our selection of these settlements. These settlements can reflect the universal laws of the spatial layout of military settlements of different levels, forms, and scales. This study combined many oral interview data from residents to better understand local military settlements’ historical evolution and cultural characteristics.

4. Results

4.1. Spatial Distribution Characteristics of Military Settlements in the Hexi Corridor

4.1.1. Distribution Pattern

As its subject, this study looked at 173 military settlements in the Hexi Corridor. It used ArcGIS 10.8 to conduct average nearest neighbor and kernel density analyses. The analysis showed that the average nearest neighbor index $R$ was 0.51. The actual nearest distance $D_o$ of the military settlement was 9.3 km, the expected average distance $D_e$ was 48.3 km, the significance $P<0.01$, and the $Z$ value was −12.37. When $R<1$, it indicates that the point elements are clustered in the geographic space unit and the spatial distribution of military settlements in the Hexi Corridor is agglomerated. In order to further explore the distribution of settlements in the region, this study used the kernel density method for visualization analysis (Figure 6). It turns out that the locations of military bases in the Hexi Corridor have created several agglomeration core areas, including Liangzhou, Yongchang, Shandan, Ganzhou, Gaotai, and Suzhou. Yongdeng (Ancient Zhuanglang Road) in the eastern part of the Hexi Corridor is relatively independent and distributed in a point-like cluster. The military settlements in Liangzhou, Ganzhou, Suzhou, and other places from east to west are closely connected, and a cluster distribution belt is formed by multiple point-like core areas. The settlement distribution trend is consistent with the Great Wall and water systems, forming a beneficial interactive relationship. There are fewer military settlements in the western region, and the distribution is relatively sparse.

4.1.2. Spatial Autocorrelation Analysis (Global Moran’s I)

This study uses the Global Moran’s I tool in ArcGIS to conduct a global spatial autocorrelation analysis of the distribution density of military settlements at the district and county levels and construct spatial relationships based on the inverse distance weighted method. The results show that the p-value equals 0.000, less than 0.01; the Z score is 3.739, greater than the critical value of 2.58. With a 99% chance of being correct, this result shows that the null hypothesis of “data presenting spatial random distribution“ can be thrown out completely. Moran’s I index is 0.269, which is greater than 0, indicating that the distribution density of military settlements in the region has significant agglomeration distribution characteristics.

The Anselin Local Moran’s I tool was used to conduct a local spatial autocorrelation analysis of the distribution density of military settlements at the district and county levels; this was performed to look at the spatial correlation between each spatial unit and its neighboring units. A LISA spatial cluster map was made (Figure 7), showing that the number of military settlements forms a high-density cluster in the Ganzhou Area and Linze County. During the Ming Dynasty, both the Ganzhou Area and Linze County were directly under the jurisdiction of the Town City. The distribution density of military settlements in this area is high, and the distribution density in the surrounding areas is also high. In Jinta County, Sunan Yugur Autonomous County, Minle County, and Jinchuan County, around the location of the Town City, a low-high agglomeration is formed; that is, the density of military settlements in the area is low, and the density in the surrounding areas is high; this shows that the town plays a core role in distributing military settlements in the surrounding areas. Many military settlements combined with the mountain terrain form a semi-enclosed ring distribution centered on the town city. In addition, Yongdeng County has formed a high-low agglomeration; that is, the density of military settlements in the region is high, while the density in the surrounding areas is low. Gaolan County and Yuzhong County show a low–low distribution. This situation demonstrates the dense distribution of military forces in Yongdeng County. However, the spatial linkage between its military resources and those surrounding Gaolan County and Yuzhong County is weak.

4.2. Environmental Characteristics of the Distribution of Military Settlements

4.2.1. The Impact of Geographical Factors on the Spatial Distribution of Military Settlements in the Hexi Corridor

The specific geological and hydrological conditions and other geographical environments are important factors in the site selection of military settlements and the development of military activities. Suitable topography is an important guarantee for constructing military settlements and related facilities. The altitude in the study area is between 805 and 5826 m. The altitude of local military settlements is distributed between 1000 and 3200 m. To examine the impact of the natural environment, this study divides the settlement points into five levels, each with an altitude of 440 m. In the Hexi region, this study shows how the geographical environment and the locations of military bases are related by exploring the relationship between the two (Figure 8).

Table 7. Statistics of military settlement elevation information.

Elevation (m)	Number of Settlements	Proportion
1000–1440	47	27.17%
1441–1880	69	39.88%
1881–2320	42	24.28%
2321–2760	14	8.09%
2761–3200	1	0.58%

Source: Statistics and plotting by the author.

reveals that plains and basins with an altitude of 1000–2320 m primarily host military settlements. There are 158 military settlements in this range, accounting for 91.33%. Among them, the highest proportion of distribution is in the 1441–1880 m interval, accounting for 39.88%, followed by the 1000–1440 m interval and the 1881–2320 m interval, accounting for 27.17% and 24.28%, respectively. There is only one military settlement in the 2761–3200 m interval, accounting for 0.58%. Although the overall elevation difference in the distribution of military settlements in the Hexi region is 2156 m, the difference is large. However, the continuity of the settlement elevation is good, indicating that the site selection of the settlement gradually rises with the terrain, which is in line with the layout principle of “following the terrain”.

4.2.2. The Influence of Water System Factors on the Spatial Distribution of Military Settlements in the Hexi Corridor

The Hexi Corridor is one of the world’s typical arid and semi-arid regions [79]. To meet the needs of soldiers for defense, daily life, and agricultural irrigation, proximity to water has become a prominent feature of settlement site selection. This study set up a five-level buffer zone and counted the number of military settlements in each level: 0–1 km, 1–3 km, 3–6 km, 6–12 km, and above 12 km (Figure 9). The goal was to find out how the location of settlements in the Hexi region related to the distance to water systems. According to

Table 8. Statistics on the number of couplings between settlement location and water system buffer zone (source: drawn by the author).

Buffer Zone Range	Number of Settlements	Proportion
0–1 km	56	32.37%
1–3 km	45	26.01%
3–6 km	27	15.61%
6–12 km	32	18.50%
Over 12 km	13	7.51%

Source: Statistics and plotting by the author.

, there are 56 military settlements distributed within the 0–1 km range, accounting for about 32.37% of the total; within the 1–3 km range, there are 26.01%; the number of settlements within the 3–6 km and 6–12 km ranges are 27 and 32, accounting for 15.61% and 18.50%, respectively; in addition, only 13 settlements are beyond the 12 km buffer range, accounting for 7.51%. War geography believes it is ideal for settlements to be located within 10 km of a water system, which can balance water use in war and reduce direct vulnerability. At the same time, this distance can effectively strengthen military defense and logistical support [32]. In the region, nearly 75% of military settlements are within a buffer range of 0–6 km from a water system. Most settlements are located within a 10 km buffer zone. Therefore, the relationship between military settlements and water systems in the Hexi region is quite close.

4.2.3. The Influence of Oasis Factors on the Spatial Distribution of Military Settlements in the Hexi Corridor

An oasis is the product of water resources in arid desert areas. The amount of water resources primarily determines the size and changes in oases [80]. Different studies have shown that desertification caused by the development of water and land resources is closely related to the rise and fall of ancient oasis towns [81,82]. Exploring the relationship between oasis and military settlement construction will help us more comprehensively understand the distribution characteristics of military settlements in the Hexi Corridor.

According to Table 8, nearly half (85) of the military settlements are in oasis areas; 42 settlements are in the 0–1 km buffer zone of the oasis, while settlements in the 1–12 km buffer zone account for only 12.72%, and settlements outside 12 km account for 13.87%. The 1 km buffer zone of the oasis concentrates nearly three-quarters of the settlements, demonstrating a high degree of spatial coupling (Figure 10a). We tabulated and visualized the 85 existing and 88 disappeared settlements in the oasis buffer zone (

Table 9. Statistics on the coupling quantity between settlement location and oasis buffer zone.

Buffer Zone Range	Number of Settlements	Proportion	Settlement Status	Buffer Zone Range	Number of Settlements	Proportion
Inside the oasis	85	49.13%	Remaining	Inside the oasis	33	38.82%
0–1 km	42	24.28%		0–1 km	20	23.53%
1–3 km	8	4.62%		1–3 km	4	4.71%
3–6 km	12	6.94%		Over 3 km	28	32.94%
6–12 km	2	1.16%	Vanished	Inside the oasis	52	59.09%
Over 12 km	24	13.87%		0–1 km	22	25.00%
				1–3 km	4	4.55%
				Over 3 km	10	11.36%

Source: Statistics and plotting by the author.

and Figure 10b). The existing settlements in the oasis accounted for 38.82%, and the disappeared settlements accounted for 59.09%; the existing settlements in the 0–1 km buffer zone accounted for 23.53%, and the disappeared settlements accounted for 25.00%. The existing settlements in the buffer zone of more than 3 km accounted for 32.94%, and the disappeared settlements accounted for only 11.36%; this shows that although the oasis is a key factor in the site selection of military settlements, the rise and fall and survival of settlements are also affected by other factors. Further study is needed on the relevant influencing factors in the future.

4.2.4. The Impact of the Great Wall’s Military Defense on the Spatial Distribution of Military Settlements in the Hexi Corridor

The coupling of military settlements and the spatial layout of the Great Wall formed a complex and multi-level overall defense system [43]. This study presented the military defense system of “Town City-Wei City-Suo City-Bao City”. The research discovered that the placement of military bases is linear and not fully in sync; this creates a multi-level hierarchical defense system that works better and protects more. According to

Table 10. Statistics on the number of couplings between settlement locations and the Great Wall buffer zone.

Buffer Zone Range	Number of Settlements	Proportion
0–3 km	86	49.71%
3–6 km	12	6.94%
6–12 km	18	10.40%
12–24 km	29	16.76%
Over 24 km	28	16.18%

Source: Statistics and plotting by the author.

, 66.69% of military settlements are located within the 12 km buffer zone of the Great Wall. Among them, 49.71% are located within the 0–3 km buffer zone, showing high spatial coupling. Figure 11 illustrates the linear distribution of military settlements along the Great Wall. Pass City, as the most concentrated defense stronghold on the Great Wall defense line, is mostly located in dangerous areas; Bao City is extensively distributed linearly along the Great Wall; Wei City and Suo City have a high degree of spatial coupling with the Great Wall and are distributed in a point-like manner. Bao City has a low degree of coupling with the Great Wall, showing discontinuous agglomeration. Military forts have a high degree of coupling with the Great Wall, showing highly consistent linear agglomeration characteristics. In addition, military forts have formed surroundings and guarding spatial layouts radiating from the Town City.

4.3. Spatial Morphological Characteristics of Military Settlements

4.3.1. Analysis of Morphological Characteristics

This study analyzed the differences in perimeter $P$, area $A$, and aspect ratio $\lambda$ among 85 military settlements in the Hexi region through box plots and histograms. The box plots show the relatively concentrated settlement perimeter, area, and aspect ratio data distribution (Figure 12a–c). The perimeter and area are left-skewed, with medians of 915.87 m and 46.51 km², respectively. The group has many outliers, indicating that the scales of settlements of different levels vary greatly. The median aspect ratio is 1.25, close to the box’s center, with few outliers; this shows that most settlements are square or nearly rectangular. The frequency histogram (Figure 12d) with the geographical distribution map of towns of varying sizes (Figure 12e) indicates that 85% of the villages possess a perimeter of less than 2000 m, predominantly consisting of low-level Bao City, which is arranged linearly along the Great Wall. More than half of the settlements are below 1000 m, while settlements with a circumference of 2000–8000 m only account for 15.02%, and there is a fault in the 5000–6000 m range. Most settlements with a circumference of 2000–5000 m are in Wei City and Suo City, which are dotted near the Great Wall and serve as military commands. There are only three settlements with a circumference of 6000–8000 m, which are of a high level and far from the Great Wall. They are Ganzhou, Suzhou, and Liangzhou, the political and economic centers of military settlements in the Hexi region.

The overall spatial characteristics of military settlements were quantitatively analyzed using the settlement morphology index (

Table 11. Analysis of the morphological characteristics of military settlement boundaries in the Hexi Corridor region.

Settlement Hierarchy	Name	Length (m)	Width (m)	λ	P (km)	A (km2)	S	Boundary Characteristics
Town City	Ganzhou	2140.50	1836.06	1.17	7.60	3515.92	1.13	Clustered settlements
Wei City	Liangzhou	2326.83	1345.98	1.73	7.18	2724.73	1.11	Clustered settlements with a tendency to banded
	Suzhou	2255.64	1005.54	2.24	6.32	1749.66	1.09	Band-shaped settlement
	Shandan	1214.04	1039.17	1.17	4.46	1239.78	1.13	Clustered settlements
	Zhenfan	1021.54	920.65	1.11	3.78	862.17	1.13	Clustered settlements
	Yongchang	1240.54	1045.80	1.19	4.52	1264.81	1.13	Clustered settlements
	Zhuanglang	1205.68	641.19	1.88	3.52	663.81	1.10	Clustered settlements with a tendency to banded
	Shazhou	1204.51	947.78	1.27	4.07	931.97	1.12	Clustered settlements
Suo City	Zhenyi	663.75	600.71	1.10	2.43	368.07	1.13	Clustered settlements
	Gaotai	958.11	764.75	1.25	3.16	595.99	1.12	Clustered settlements
Bao City	Aba	409.83	293.30	1.40	1.38	116.61	1.12	Clustered settlements
	Dongle	571.70	247.29	2.31	1.60	129.18	1.08	Band-shaped settlement
	Hongchengzi	434.69	297.19	1.46	1.37	118.22	1.12	Clustered settlements
	Hongshui	738.84	695.77	1.06	2.78	457.06	1.13	Clustered settlements
	Qingshui	403.54	347.95	1.16	1.35	119.43	1.13	Clustered settlements
	Liuba	351.71	325.16	1.08	1.29	104.20	1.13	Clustered settlements
	Shixiakou	510.90	223.37	2.29	1.43	108.97	1.09	Band-shaped settlement
	Wusheng	289.58	210.13	1.38	0.99	59.85	1.12	Clustered settlements

Source: Statistics and plotting by the author.

). The findings show that the morphology index $S$ stays around 1.10, and most settlements have an aspect ratio of $\lambda <1.5$, clearly showing that they are grouped. From the perspective of the hierarchy system, both town cities and fortresses have cluster characteristics; the acropolis and fortresses are mostly cluster settlements, and only some settlements have a strip tendency or present a band-shaped feature. Specifically, the aspect ratio of Liangzhou and Zhuanglang is $1.5\le \lambda <2$, a cluster settlement with a strip tendency. Suzhou, Dongle, and Shixiakou show the characteristics of band-shaped settlements and their aspect ratio, $\lambda \ge 2$. Combined with satellite data, the settlement land use morphology of military settlements in the Hexi region is relatively regular, the spatial layout is relatively compact, and most settlements are square or rectangular. They are nested and expanded on this basis. At the same time, compared with the military defense performance, the natural geographical environment has less impact on settlement morphology.

According to the analysis results, Suzhou’s morphological index $\lambda$ is 1.73. The research team found in the field survey that this result is mainly due to the expansion of Guancheng on the east side of Suzhou. The surrounding mountainous environment significantly influenced the construction of a few settlements, including Qingshui and Zhuanglang. One is in a canyon, and the other is in an area with mountains on both sides. The villages’ shapes are limited by these mountains, and the natural features around them have come together to form a band-shaped layout.

4.3.2. Space Syntax Analysis

Many studies have shown that the axis analysis method in space syntax can effectively reflect the spatial structure of settlements. This study selected three variables, integration, intelligibility, and connectivity, to describe the spatial morphological characteristics of settlements from the perspectives of accessibility, spatial cognition, and spatial permeability. In drawing the axis map, this study used the Keyhole satellite images from the 1960s–1970s as a reference and conducted an axis analysis on the streets extracted from the above 18 typical military settlements. Today’s increasingly modernized world has replaced the original spatial patterns of many military settlements in the Hexi Corridor. The settlements in the Keyhole satellite images maintain the original street and lane spatial texture. Matching and checking with historical maps can become a basis for studying the spatial morphology of military settlements in the Ming and Qing dynasties.

(1) Integration Analysis:

The average integration of the 18 military settlements ranges from 1.06 to 1.75 (

Table 12. An analysis of the space syntax parameter values of typical military settlements in the Hexi Corridor.

Settlement Hierarchy	Name	Number of Axes	Global Integration Value		Intelligibility Value	Mean Depth	Connectivity Value
			Max	Average
Town City	Ganzhou	97	2.69	1.56	0.55	3.83	2.97
Wei City	Liangzhou	96	2.77	1.49	0.64	3.91	3.31
	Suzhou	110	2.74	1.39	0.47	4.26	3.02
	Shandan	46	3.56	1.75	0.90	2.91	3.61
	Zhenfan	34	1.98	1.14	0.75	3.66	3.06
	Yongchang	72	3.16	1.63	0.70	3.40	2.92
	Zhuanglang	67	2.03	1.12	0.63	4.39	2.83
	Shazhou	39	2.60	1.40	0.82	3.22	3.49
Suo City	Zhenyi	40	1.89	1.18	0.79	3.71	3.20
	Gaotai	39	2.43	1.35	0.64	3.31	2.72
Bao City	Aba	22	1.88	1.06	0.42	3.16	3.27
	Dongle	33	2.50	1.19	0.59	3.39	2.59
	Hongchengzi	41	2.87	1.30	0.63	3.41	2.83
	Hongshui	63	2.50	1.28	0.66	3.92	2.70
	Qingshui	20	2.41	1.47	0.85	2.49	3.30
	Liuba	29	2.58	1.33	0.74	3.02	2.83
	Shixiakou	26	3.92	1.60	0.57	2.60	3.08
	Wusheng	16	1.88	1.06	0.82	2.84	2.63

Source: Statistics and plotting by the author.

). The average integration of Town City and Wei City is 1.12 to 1.75. Among them, 75% of the settlements have a road network integration higher than 1.35, indicating their road network accessibility is relatively high. Ganzhou (Figure 13a), Shandan (Figure 13b), and Yongchang (Figure 13c) have large areas, complete road networks, and integration higher than 1.55. Shandan has the highest integration (1.75), outstanding internal transportation potential, and high recognizability. In contrast, Suo City and Bao City have low integration (1.06 to 1.60), most lower than 1.35, and their spatial recognizability is relatively weak. Aba (Figure 13k) and Wusheng (Figure 13r) have the lowest integration (1.06), while Shixiakou (Figure 13q) is the settlement with the highest spatial recognition in the Bao City (integration 1.60), which is strip-shaped with only one axis running through the north and south. The main axis closely relates to the alleys.

The highest integration value of medium and high-level settlements (Town City, Wei City, and Suo City) is on the north–south central axis, and most of them are cross-shaped (Figure 13a–j), with main roads derived from the axis forming a checkerboard-like spatial pattern. Bao City is small in area and has limited street development, so it is mostly characterized by a single axis, which radiates from the central axis to other streets (Figure 13k–r). Despite this, the military settlements in the Hexi region all use the main axis as the core gathering area for human activities, and this spatial organization logic is consistent in settlements at different levels.

(2) Intelligibility Analysis

Table 11 shows that the intelligibility values of military settlements in the Hexi region are between 0.42 and 0.90. Most of the settlements have $R^2$ values higher than 0.50, which means that the internal spatial units are closely linked, and the global spatial structure can be understood at the local level. Among them, the $R^2$ values of Shandan (Figure 14d) and Shazhou (Figure 14h) are 0.90 and 0.82, respectively, which are the highest among high-level settlements. Although there is a trend in boundary expansion between the two, the road network planning is unified, with the cross-shaped axis as the central street, supplemented by the layout of long streets and small lanes; the increase in the number of city gates improves connectivity and significantly improves spatial intelligibility. Among the Bao Cities, Qingshui (Figure 14o) and Wusheng (Figure 14r) have the highest $R^2$ values, which are 0.85 and 0.82, respectively. Their lanes intersect and run through the main axis in a cross shape, which enhances their spatial cognition. However, Aba (Figure 14k) is divided into inner and outer cities, with poor visual coherence and road network connectivity, and the $R^2$ value is only 0.42. In addition, Ganzhou (Figure 14a) and Suzhou (Figure 14c) have low comprehension values ($R^2$ values are 0.55 and 0.47, respectively). It may be that the complexity of the internal laneways conflicts with the efficiency of the main street, increases the difficulty of local recognition of the whole, and reduces spatial intelligibility.

(3) Connectivity analysis

Connectivity reflects the number of intersections between a space and other spaces in a settlement system. The larger the value, the closer the connection in the area and the higher the functional importance. The connectivity of the 18 military settlements ranged from 2.59 to 3.61 (Table 11). Among them, Shandan and Shazhou had the highest connectivity (3.61 and 3.49, respectively). Their mesh road network morphology reflects excellent connectivity and openness. Many long streets and main axes run through the settlement, providing convenient transportation. In contrast, Dongle and Wusheng had the lowest connectivity (2.59 and 2.63, respectively). The north–south axis primarily concentrated on internal traffic, while the surrounding roads could not alleviate traffic flow.

5. Discussion

5.1. Spatial Distribution Pattern of Military Settlements Along the Ming Great Wall

5.1.1. Consideration of Natural Factors in the Site Selection of Military Settlements

This study focuses on Northwest China. The way military bases are spread out in the Hexi Corridor differs from what Du Yumin et al. (2021) found when they looked into military bases in Qinghai [83]. They found that bases are spread out in a central radial pattern. The complex mountain terrain of the Hexi Corridor has led to the overall linear arrangement of military settlements with multiple military centers. Military settlements are mostly located in plains and basins with strong spatial agglomerations. In the 12th year of Hongwu (1379), Emperor Taizu of the Ming Dynasty moved the Shaanxi Xingdu Command to Zhuanglang. Later, due to the inefficiency of the management of the military forces in Gansu Town, the organization was moved westward to Ganzhou; this also explains why the military settlements in Ganzhou, Linze, and Yongdeng were the most densely distributed and reflects the core strategic position of the town in the military defense system of the Hexi region in the Ming Dynasty and the court’s review of the strategic position of Gansu Town. This distribution pattern also indirectly reflects the strong control over the surrounding areas of town cities, the strong military force, and the perfection of the defense system.

In terms of influencing factors, environmental factors are multifaceted and closely related to topography, water systems, and oases.

(1) Water sources are the first criterion for selecting military settlement sites. The distribution of military settlements in the Hexi Corridor confirms Li Yan et al.’s (2020) view: military settlements are ideally located within 10 km of water systems [84]. Military settlements built by water have spatial consistency with oases rich in natural resources. Most military settlements are located along the oases on both sides of the Shuzhuang River branches. An adequate water supply can provide soldiers with water for living and agriculture and increase the duration of military stationing. In urban planning, some settlements divert water to form moats, using rivers as natural barriers for military defense to enhance the city’s defense capabilities.

(2) Wang Linfeng (2018) confirmed the defensive idea of the Jizhen military settlements by building strategic locations in the mountains through GIS research [11]. First, the high-altitude mountains on both sides of the Hexi Corridor form a natural defense line, reducing defense pressure. Second, high ground is often used as a lookout point and fortification site. It has a wider field of view and more rugged terrain, which is convenient for defense and easy to control surrounding areas. Finally, the complex terrain limits the choice of transportation routes. Military settlements near major transportation routes facilitate military mobilization and resource transportation.

Some settlements are distributed in river valleys with lower altitudes. Zhuanglang Road is located in the eastern part of the Hexi Corridor (Figure 15a) and is generally surrounded by water and mountains. In the middle of the Ming Dynasty, the imperial court passively defended. From Chenghua to Zhengde (AD. 1465–1521), Mongolian tribes frequently invaded Zhuanglang, and wars broke out frequently. Military settlements, mountains, side walls, and piers formed a multi-level defense space, guarding and controlling the main land transportation routes to resist invasion. Mountains surround Yongchang (Figure 15b). The inland rivers and oases host military farms. The fertile land and sufficient irrigation around Ganzhou (Figure 15c) are conducive to the large-scale garrison of the army. At the same time, the mountain systems on the north and south sides have largely avoided the risk of war in the town. Ganzhou is in the middle of the Hexi Corridor between Liangzhou and Suzhou. It has the transportation advantage of connecting the East and the West, which is more convenient for military command. It is an excellent strategic location for the Gansu Town Defense Zone.

5.1.2. Strategic Thinking Reflected in the Distribution of Military Settlements

In the fifth year of Hongwu (1372), Emperor Taizu of the Ming Dynasty sent troops to wipe out the remnants of the Yuan Dynasty in Gansu, all the way to Guazhou (now Anxi, Gansu) and Shazhou (now Dunhuang, Gansu), forming the initial territorial pattern of the Ming court in the northwest. In addition, there were Mongolian forces in the north of the Hexi Corridor and various foreign forces in the west. Emperor Taizu of the Ming Dynasty established Gansu Town (one of the nine important towns of the Ming Dynasty) in the Hexi Corridor, which effectively alleviated the military crisis of the Ming Dynasty. The Hexi region distributes its various defense zones in a belt-like pattern. The defense system they constitute is not a passive linear defense barrier. Instead, the Great Wall, military settlements along its path, and military facilities form a dynamic defense system. The construction of this defense system is consistent with many areas along the Ming Great Wall [10,15]. It includes Town City, Wei City, Suo City, grassroots fortresses, and military facilities. The settlements in the defense zone are arranged clearly, creating a multi-level defense structure (Figure 16). This multi-layer structure is like the distribution pattern of military settlements in Datong Town [85]. The vertical hierarchical structure reflects military defense’s rigor, integrity, and continuity.

The forts along the Ming Great Wall were small and distributed in a belt-like pattern. They were mainly responsible for guarding the border walls and mountain passes. Smaller forts took the lead in battles. Suo City, Wei City, Town City, etc., responded in turn to transport troops, supply materials, and make strategic plans. The highest-level town city was responsible for overall military command and jointly resisted foreign enemies; this reflects the improvement in the military management system in the Ming Dynasty and the objective needs of military defense.

5.2. Spatial Morphological Characteristics of Military Settlements Along the Ming Great Wall

5.2.1. Isomorphic Characteristics of Spatial Units in Military Settlements

He Ding et al. (2023) focused on the composition of the waterscape of military settlements along the Great Wall of Beijing [86]. Although Tuo Xiaolong and Li Zhe (2022) focused on the spatial morphology of ancient cities in Northwest China [87], they did not elaborate on their space’s organizational relationship and internal logic. This study further analyzed the isomorphic characteristics of its spatial units by analyzing the spatial morphology of settlements. The military settlements in the Hexi Corridor are based on square geometric units and adopt nested and superimposed spatial organization methods. The square of a single building (Figure 17a) is the basic frame unit of the settlement. Geometric elements can be spatially isomorphic, which gives the building of the settlement a centripetal spatial order in form. The single building’s vertical changes and symmetrical layout form a courtyard-style courtyard (Figure 17b); the axial superposition forms a multi-entry courtyard (Figure 17c), expanding the usable space and functional divisions. Figure 17d shows the endogenous logic of the street space, which comprises a complex cluster of single buildings and courtyards. The central axis of the settlement is connected to it to make small and medium-sized settlements (Suo City, Bao City). As the scope of the settlement land expands, the long street is added to form multiple square partitions, which improves the spatial order of large settlements (Wei City) (Figure 17f). The isomorphic order of square elements runs through all stages of development, from buildings to settlements; this makes the building space, courtyard space, street space, urban axis, and long street work together naturally.

The settlement’s centralized and hierarchical spatial order is based on basic spatial units constantly stacked on each other. The axial organization form creates an organic whole from scattered volumes, achieving both centripetal and axial layouts. This layout method gives the settlement an introverted defensive characteristic, which meets the needs of physical defense and resource assembly and reflects the spiritual defense needs of the military and civilians.

5.2.2. The Internal Street and Lane Texture of Multi-Level Military Settlements

The qualitative study by Ma Ming and Sun Yifu (2017) pointed out that the spatial layout of the military settlements along the border of Jin and Meng has the characteristics of a cross-shaped and straight-line layout [38]. This study further supports the above view using space syntax and explains the correlation of military settlement space from a quantitative perspective.

The spatial layout of military settlements highlights the top–down planning and hierarchical characteristics. Town City, Wei City, Suo City, and Bao City show differences in scale and function according to their levels. The large and medium-sized military settlements (Town City, Wei City, and Suo City) in the Hexi region have obvious axes and a complete road network system. The road system exhibits a multi-level structure consisting of central streets, long streets, and narrow lanes. The long streets of the north–south and east–west crisscross to form a regular grid layout like a chessboard. The settlement’s central area has the most accessibility and is the most dynamic; this is similar to the conclusion of Wang Jingwen and Wang Zhongyu (2019) regarding the military garrison in Anshun City, Guizhou Province [88].

Town City is the core of military command and has multiple functions, such as military, political, and economic. The internal roads, including the central street and the long street, constitute the main traffic space of the city. The intersection of the streets is the city and commercial center. The lanes are the living space for the military and civilians. Although irregular, they provide convenience for the small-scale lives of the military and civilians, forming a spatial order familiar to the locals. The main function of Wei City is to station troops and store grain, and its economic function is relatively weak. Its internal traffic is a cross-shaped road structure, presenting a multi-level structure. The roads in Suo City have cross-shaped axes and long streets with fewer lanes. The internal road network of Bao City is primarily structured as a “central street-narrow lane”. It mainly comprises garrisons, and it is a complete military facility. Some cities (such as Hongshui) are larger, with a cross-shaped axis and multi-level road network.

5.2.3. Strategic Thinking Reflected in the Zoning Planning of Military Settlements

Although the research conducted by Li Yan et al. (2020) revealed the functional elements of military settlements [84], it rarely elaborated on their functional layout and the power symbol behind them. Settlements were built in a way that made sense because of military defense and the Lifang system; this is a physical sign of power that has order and gradualness. How resources are divided into the hierarchical system, how people are managed in the Lifang system, and how functions are set up all show how power is concentrated and how people directly control social space.

From the perspective of spatial layout, the distribution of various functional buildings in the settlement has a circle-like characteristic. Its distribution from the center of the settlement to the edge is roughly presented as building towers, administrative buildings, religious buildings, cultural and educational buildings, and military buildings and facilities (Figure 18). Building towers are mainly located at the intersection of the central axis of the settlement and above the city gate. They are generally the tallest buildings in the fort and serve as city landmarks. Administrative and military buildings are usually located near the main roads in the core area of the settlement, with excellent accessibility and reflecting official authority. Most cultural and educational buildings cluster in a corner of the city, often in groups of three or two, exhibiting a point-like aggregation characteristic. Military facilities and buildings are mostly close to the corners of a city wall, which is convenient for quickly forming a coordinated defense with military forces, such as city walls and corner towers. In addition, buildings can only be physically defensive for the military and civilians who are constantly at war, while faith brings spiritual comfort [89]. The military and civilians spread religious buildings throughout the settlement to meet their spiritual needs. Buildings such as Buddhist and Taoist temples embody different beliefs and symbols and meet spiritual demands, such as breeding offspring, worship, and fighting will.

5.3. Construction of Defense Mechanism of Internal Spatial Form of Military Settlements

Numerous studies on military settlements along the Ming Great Wall focus solely on the defense mechanisms within their distribution pattern [90,91]. They ignore the defense mechanism of single settlements and their internal spatial form. This study attempts to reveal the construction of the defense mechanism of the internal space of military settlements from the perspective of settlement and internal street forms.

The city wall primarily determines the boundary morphology of military settlements in the Hexi region, with the terrain having less influence. Most of them are regular quadrilaterals. The ancient well-field system and the city-building ideas in Zhou Li Kao Gong Ji influence their basic form. The military settlements are mostly cluster-shaped, and some are strip-shaped or have a strip-shaped tendency. In the Ming Dynasty, the urban pattern changed from the closed Lifang system to the open street and alley system, but the military settlements still maintained the closed Lifang system’s space form due to defense needs. The city wall is the core defense facility of the military settlement. The city wall surrounds the settlement and facilitates communication with the outside world through the city gate. Due to insufficient land, some settlements expanded the Pass Fortress (Figure 19a) outside the city or built a square or semicircular Barbican Entrance (Figure 19b) at the city gate to enhance defense capabilities and protect the safety of the main city. This layout is a nested structure based on strategic needs, which differs from traditional villages’ construction models.

The defensive function construction of the internal spatial form of the military settlements in the Hexi region is reflected in the efficient military resource distribution of its overall space and the intricate internal spatial structure of its local streets and alleys. This spatial structure, both disorderly and orderly, effectively reflects the functionality of military defense. Large military settlements adopt a chessboard-like road network layout to form an efficient transportation system. This layout considers daily life and military defense needs, facilitating the assembly of soldiers and the transportation of supplies. This layout provides a convenient path for coordinated defense between settlement units during combat. The grid road divides the local space, combining small alleys into “T” and “L” shapes to create narrow, multi-turning alleys. This spatial structure familiarizes local military personnel and civilians but makes outsiders lost. Take Wuwei City (ancient Liangzhou Wei City) in 1943 (Figure 20) as an example. The city maintained the overall pattern of the Ming and Qing Dynasties, with clear street texture. In the local space, short, narrow, and multi-turning small-scale alleys replaced the long, straight roads in the main street; this effectively shortens the line of sight, disperses enemy forces, and facilitates interception and resistance.

5.4. The Connotation of Fortification Wisdom in Military Settlements Remains Consistent

This study found that although military settlements have obvious differences in many aspects, their spatial genes are the same and have a certain spatial paradigm inheritance. This study found that their spatial genes are the same and have cultural inheritance. American scholar Kevin Lynch believes the square city is a typical Chinese urban model. Its enclosure and symmetrical layout embody the combination of ritual and space, manifesting the harmony between man and nature [92]. Military settlements in the Hexi Corridor region mostly adopt the square city form, which needs military defense and reflects the traditional Chinese concept of heaven and earth. China’s fortification culture began in the Late Yangshao (3500–3000 BC) [93]. The shape of the ancient city gradually changed from round to square, and many city walls began to appear, becoming a unified model for the design of ancient cities later (Figure 21) [15]. The square city is easy to defend and can effectively limit the direction of enemy attack. From the Yangshao culture to the Ming and Qing dynasties, Chinese cities continued the city-building experience of prehistoric and ancient times.

Hillier Bill and Hanson Julienne (1989) pointed out that spatial morphological characteristics are used as phenotypes, and the abstract principles that generate these spatial morphological characteristics can be regarded as the genotype of space [95]. The military settlements along the Ming Great Wall in the Hexi Corridor have an internally consistent spatial organization form and genotype; their genotype is homogeneous; this includes city walls, urban axes, chessboard layouts, and functional buildings. Settlements of different sizes and functions have different distribution locations and construction methods. Single military settlements show heterogeneous spatial forms, but their generation logic is based on this genotype. This internal spatial order is the inheritance of China’s city-building wisdom and planning practices since the Zhou Dynasty, forming a clear spatial paradigm (Figure 22a). The square city walls, chessboard-shaped roads, and central buildings of the Hexi Corridor military settlements (Figure 22c) all have features similar to the strict hierarchy and structure of Chinese ritual thought. The spatial form formed by the military settlement not only manifests itself as a hierarchical order in urban layout and architecture but also internalizes this order into the social system.

6. Conclusions

This study used GIS methods and space syntax to reveal military settlements’ distribution patterns and spatial morphological characteristics from a “macro–meso–micro” system. The GIS method realizes the quantitative expression and visualization of military settlements’ spatial distribution patterns and accurately identifies settlements’ spatial agglomeration characteristics and their coupling relationship with environmental factors. Space syntax focuses on the organizational logic of the internal spatial structure of settlements and quantifies the spatial utilization rate of military settlements. The combination of the two not only constructs a multi-scale research framework of “macro-distribution–meso-morphology–micro-functional elements”, but also explains the co-evolution mechanism of military settlements, natural geography, and defense systems from a spatial dimension, providing a theoretical basis that is both scientific and cultural for the holistic protection of linear military heritage.

The main research findings include the following: (1) Due to natural conditions and military defense needs, the military settlements in the Hexi Corridor are distributed in a linear belt along the water system and the Great Wall. They are mostly located in oasis areas with low altitudes, mainly plains and basins. The site selection focuses on resource sustainability and military security. There are differences in the spatial coupling between settlements with different levels and the Great Wall. (2) The boundary of military settlements is regular, mostly in regular quadrilaterals, with obvious cluster characteristics. A few settlements are strip-shaped settlements and cluster-shaped settlements with strip-like tendencies. Its spatial structure is compact, and the transportation network is multi-level. The central axis of the settlement has the highest accessibility and is the core of population gathering. Overall, spatial cognition is high. (3) The functional zoning is unified, scientific, and strategic. Building towers are located at the intersection of the central axis; administrative buildings are at the core. Religious buildings are scattered throughout the settlement, cultural and educational buildings are concentrated in one corner, and military buildings are close to the city wall for rapid defense. (4) The military defense system mainly affects settlements’ spatial distribution and morphology. The horizontal linear distribution along the Great Wall and the vertical management system ensure the timeliness of military resource investment and command efficiency. The square boundary limits the direction of attack, and the chessboard-like road network improves the efficiency of resource allocation. The “T” and “L” shaped structures of the lanes embody the internal space defense of the settlement. The internal mechanism guides this external space representation, precisely embodying the strategic defense wisdom of the military settlement.

However, this study has certain limitations. First, the sample covered in this study is limited, involving only military settlements in the Hexi Corridor region, and it does not cover the entire Gansu Province or other areas along the Ming Great Wall. In the future, expanding the sample to improve the research system and provide a more comprehensive reference for settlement distribution and cultural relics protection will be necessary. Second, although the spatial morphological characteristics of military settlements were analyzed through integration and comprehensibility, these indicators cannot fully reflect the spatial usage and military defense performance of the century. In the future, it is necessary to combine more historical data, such as the number of garrisons and battles, to demonstrate further. Finally, the historical data of this study are limited. The buffer zone set refers to existing research and walking accessibility but does not verify historical military systems (such as marching speed and the range of garrison activities). At the same time, due to the limitations of the subject and data, the driving mechanism of the survival of oasis settlements has not been deeply explored. Future research can combine historical geography, environmental archeology, and demography to optimize the buffer zone model, reveal the internal motivation of settlements’ temporal and spatial evolution, and enhance the historical rigor and mechanism explanatory power of the spatial analysis of military heritage.