Introduction

The state of Goguryeo (37 BCE – 668 CE) was founded in the northwestern reaches of the Korean Peninsula, in the Jolbon region (present-day Benxi, Huanren County, Liaoning Province, China). Goguryeo had instituted a centralized system of government by the first century CE, at which time the rulers moved its capital to Gungnae Fortress (present-day Ji’an, Jilin Province, China); by the fourth century, it had emerged as one of the four great powers of East Asia. In 427, the capital was moved to Pyeongyang Fortress, and from this time on the state intensified its southern expansion. The pinnacle of Goguryeo’s power came in 475, when its forces conquered the Baekje capital of Hanseong (漢城). At its peak, Goguryeo territory stretched from the northeast region of present-day China to the central and southern regions of the Korean Peninsula. Historical records have been intensively studied in order to glean information about Goguryeo’s southern expansion following the move of its capital to Pyeongyang. Even so, written materials on the subject are exceedingly scarce, so the method of this expansion, not to mention its details, remain largely in question. Fortunately, beginning in the 1980s, a number of Goguryeo sites and artifacts discovered in southern Korea have been investigated, yielding sufficient archaeological material to shed new light on the topic.

The 1979 discovery of the Jungwon Goguryeo Monument served as a catalyst for the study of Goguryeo’s southern expansion policy. In particular, the site generated considerable research on Goguryeo-Silla relations in the fifth century and on Goguryeo’ s expansion into the Chungju region. Beginning in the 1980s, tombs with structures similar to those of Goguryeo tombs were identified in southern Korea, but they could not be definitively characterized as Goguryeo tombs due to the lack of conclusive evidence. Thus, they were regarded merely as “Goguryeo-style” tombs, a perception that inhibited further research on them.

Goguryeo sites and artifacts were unearthed within Mongchon Earthen Wall Fortress in 1988, leading to a renewed interest in and investigation of Goguryeo sites in southern Korea. Then, in 1994, some 20 Goguryeo forts were identified along Mt. Acha, on the northern banks of the Han River, and the excavation of those forts began in 1997. In 1999, a series of military fortification sites were also discovered in the Imjin-Hantan River region and in the Yangju basin. Goguryeo mountain fortress sites have also been identified and excavated in the Geum River region.

More recently, since the 2000, an increasing number of “Goguryeo-style” tombs have yielded examples of Goguryeo pottery. As a result, many tombs once considered to be merely “Goguryeo-style” tombs have been reclassified as actual Goguryeo tombs. In addition, Goguryeo settlement sites have been identified in the vicinity of some of these tombs (Fig. 1). In light of these recent findings, this paper presents an overview of the research on the Goguryeo fortifications, tombs, and settlements of southern Korea, which can be regarded as evidence of Goguryeo’s southward expansion in the peninsula. Based on this archaeological evidence, the policy and actual process of Goguryeo’s southern expansion will also be examined.

Goguryeo Fortification Sites in Southern Korea

Location and Distribution of the Fortification Sites

At present, approximately 50 Goguryeo fortification sites have been identified in southern Korea, and more sites are expected to be discovered through future investigations. The fortification sites, which comprise both f latland fortresses and mountain forts/fortresses, have been found in the following four areas: the Imjin-Hantan River region; the Yangju Basin and its environs; the lower reaches of the Han River and the area around Mt. Acha; and the Geum River region.

The area including the Imjin and Hantan Rivers, which pass through Yeoncheon-gun and Paju-gun in Gyeonggi Province, is an intermediary point in approaching the Han River region from the north. Hence, approximately 20 fortification sites have been discovered along both sides of the rivers. Most of the fortifications in the Imjin River area face one another on the flatlands to the north and south of the river. Key examples of such flatland fortresses include Horogoro Fortress, Eundaeri Fortress, and Dangpo Fortress, all of which are situated on a triangular basalt plain formed by the Imjin River and its tributary, the Saet River. Two sides of the plain consist of high basalt cliffs overlooking the rivers, so a sturdy fortress wall was constructed along the plain’s third side.

Situated between the Imjin and Han Rivers, the Yangju Basin was a strategically important point for transportation, and so a number of fortification sites were built there. To date, 28 mountain forts have been identified in the area, typically along mountain ridges, in lines that follow north-south axis. The forts were built on mountain ridges that offered good views of the transportation routes that passed through the flatlands below. Some of the forts were isolated, but most were built at intervals of 500 meters, forming a linear network of forts (Fig. 2).

Located in the central part of the Korean Peninsula, the Han River region sits on the main transportation route between the northern and southern parts of the peninsula. In addition, the wide plains of this region allow easy access to the West Sea. Due to this superior geographic location, control of the region played a key role in the geopolitics of the Three Kingdoms Period (57 BCE – 668 CE). A total of 21 forts have been identified on Mt. Acha and its environs, seven of which have been or are in the process of being excavated. The forts were placed at intervals of 400-500 meters, and they were most likely linked by structures such as wooden fences or stone walls (Fig. 3).

Goguryeo fortifications identified in the Geum River region include Daemo Mountain Fortress in Jincheon, Namseonggol Mountain Fortress in Cheongwon, and the Wolpyeong-dong site in Daejeon. Excavations on sections of Namseonggol Mountain Fortress have provided relatively detailed information on the Goguryeo fortifications of this region. Notably, Namseonggol Mountain Fortress sits at the uppermost navigable point along the Geum River, a key point for transportation and logistics since ancient times. As large-scale mountain fortresses, the Goguryeo fortifications of the Geum River region are distinctive. In addition, unlike those in the three areas examined above, the fortification sites in the Geum River region are isolated, rather than arrayed in clusters.

Structure of the Fortification Sites

With the notable exceptions of Daemo Mountain Fortress and Namseonggol Mountain Fortress, both located in the Geum River region, virtually all of the Goguryeo fortification sites are small in scale (with diameters under 500 m). The majority of fortification sites consist of outer fortress walls made of stone or wood, with buildings within. During the early phases of occupation, wooden fences were often used as fortification, and stone walls were later added outside those fences. The method of constructing the fortress walls varies slightly from area to area. In the case of the flatland mountain fortresses of the Imjin River region (e.g., Horogoro Fortress, Eundaeri Fortress, and Dangpo Fortress), the walls consisted of a core of rammed clay, faced on either side with cut stone. (Fig. 4). The forts of the Han River region were constructed by erecting one or two stone walls about three to five meters in height on either side of the pre-existing wooden fence. The space between the structures was then filled with alternating layers of clay and saprolite, which were rammed or stamped.

The fortress walls of Namseonggol Mountain Fortress were built by erecting two parallel wooden fences and then packing clay into the space between. The entrances were the only parts of the fortress walls that were reinforced with stone. In order to improve their defenses, the majority of forts had additional chi (雉) structures—protruding sections of the walls that allowed soldiers to attack and defend from three sides. Some of the chi structures were built according to a different design, permitting them to be used as entrances (Fig. 5). Namseonggol Mountain Fortress also had an outer moat, which provided additional protection, as did Hongryeon Peak Fort 2.

These defensive sites included numerous buildings, in addition to water storage and drainage facilities (Fig. 6). Most of the buildings used as barracks stood above ground, although some pit dwellings have also been identified. These square or rectangular structures had gambrel roofs and walls made from a mixture of stone and clay. They usually measured five by seven meters, but some of the larger buildings could be up ten meters long and forty meters wide. The buildings contained L-shaped ondol facilities, which provided partial floor heating. This type of ondol consisted of a single flue through which heated air flowed. The flue was formed by long stone slabs, and the entire structure was plastered with a mixture of mud and straw.

All of the forts contained one or two water-storage facilities, consisting of square tanks that were carved into the weathered bedrock, with mud applied to the sides and bottom of the tanks for additional water-proofing. Wooden logs were stacked along each of the walls to form the inner face of the water tank, and the spaces between logs and walls were packed with mud. Although the overall size of the water tanks varies slightly, each held approximately the same volume of water, indicating that each fort was expected to store a similar amount of water.

The forts also included a variety of other facilities (Fig. 7). At Mt. Acha Fort 4 and at Mt. Yongma Fort 2, for example, simple blacksmith workshops were found some distance away from the main cluster of buildings; these workshops were apparently used to make simple repairs to iron implements. Structures associated with firing pottery were identified at Hongryeon Peak Fort 2, while Mt. Acha Fort 3 yielded the remains of what appear to have been a blacksmith forge, underground storage facilities, and a mill structure, with the mortar and parts of the pestle in situ. These facilities yield insight into some of the activities undertaken by the soldiers stationed at the forts. In particular, the presence of iron farming tools suggests that the soldiers must have engaged in agricultural pursuits during times of peace.

Artifacts from the Fortification Sites

Excavations carried out at the fortification sites have yielded numerous artifacts, comprising mainly pottery vessels and iron implements. The pottery can be divided into 24 types, including vessels for storage, cooking, serving and transport. Goguryeo pottery excavated from the sites around Mt. Acha typically dates to the early sixth century. The vessels were handmade using the coiling method, after which they were placed on a slow-turning potter’s wheel to smooth the surfaces. The pottery is typically brown, gray, or black in color (Fig. 8).

Large quantities of iron implements—including weapons, agricultural implements, and everyday tools and vessels—have also been discovered at Goguryeo fortification sites. The iron weapons can be divided into offensive weapons (e.g., swords, spears, axes, bows and arrows, etc.) and defensive weapons (e.g., armor, helmets, etc.). Excavations at Gueui-dong Fort, where an estimated ten soldiers were stationed, have uncovered around 3,000 arrows, for example, along with two swords, ten spears, and four battle-axes. This discovery reveals how the Goguryeo army was organized and allows us to estimate the number of weapons it may have possessed. As for defensive weapons, Mt. Acha Fort 4 yielded one iron helmet, while a suit of upper body lamellar armor was excavated at Mudeung-ri Fort 2 (Figs. 9 and 10).

Goguryeo fortification sites have also yielded numerous iron agricultural implements and tools, such as ploughshares, shovels, spades, scythes, axes, and chisels, and various vessels, including iron jars and cooking pots. In addition, a limited quantity of iron horse-gear (e.g., bridle bits, bit stoppers, stirrups, and buckles) has been discovered, suggesting that (at least) the Goguryeo army officers stationed at the forts may have used horses to traverse the mountainous terrain.

Numerous roof tiles, including some embellished with lotus patterns, were unearthed at Horogoru Fortress and Hongryeon Peak Fort 1 (Fig. 11), representing the first Goguryeo roof tiles to have been found in southern Korea. Given that Goguryeo roof tiles and roof-end tiles were used only for such public structures as palaces, temples, and administrative buildings, the presence of such roof tiles illustrates the significance of these defensive facilities. A ceramic drum sporting the two-character inscription “sanggo” (相鼓), or “small drum,” was also excavated at Horogoru Fortress; a similar ceramic drum was also found at Mt. Cheonbo Fort 2. In addition, the discovery of a gold earring at Namseonggol Mountain Fortress signals the importance of the site.

Chronology of the Fortification Sites

Given the period’s historical context, the Goguryeo fortification sites in southern Korea likely were first established around the late fourth century, just when Goguryeo intensified its policy of southern expansion. However, the morphological and technological characteristics of the pottery found at these sites indicate that the sites’ time of establishment and use differed according to region and type of fortification.

Amongst the globular jars from the Han River region—the most intensively studied area—those from the forts of Mt. Acha and its environs date to the early sixth century. On the other hand, a long-necked jar with four handles from Mongchon Fortress dates to the late fifth century, based on its morphological attributes. These chronological interpretations are supported by the discovery at Hongryeon Peak Fort 2 of a pottery vessel bearing the inscription 庚子 (gyeong ja), a date that corresponds to 520 in the Gregorian calendar (Fig. 12). Based on this interpretation, the Goguryeo forces that conquered the Baekje capital in 475 would have remained at Mongchon Fortress until around 500. The forts located north of the Han River around Mt. Acha were established around 500 and were occupied until 551.

Based on this chronological framework, the pottery from the fortification sites in southern Korea can be divided into two types based on their morphological and technical characteristics. The first type is distinguished by its black surface color, decoration of dots or concentric lines, and its base clay with sandy inclusions. The second type, which lacks decoration, has a brownish surface color and a fine base clay with no inclusions. According to chronological studies on the Goguryeo pottery of the Han River region, the first type dates from the mid-fifth to the early sixth century, while the second type dates from the early to mid-sixth century.

Both types of pottery have been found at the fortification sites of the Imjin and Han River regions. In addition, some of the sites contain pottery from an even later date, suggesting that they were occupied from the mid-fifth until as late as the midseventh century, at least in some cases. The fortification sites of the Yangju Basin are limited in number, making it difficult to ascertain the dates when they were occupied. Nevertheless, pottery from Mt. Cheonbo Fort 2 indicates that they were built after the mid-fifth century. At the same time, fortification sites of the Geum River region, such as Namseong-gol Mountain Fortress, have yielded only pottery belonging to the first type, which might imply that they were occupied only for a limited period of time. In particular, based on the nature of the pottery and the historical context of the time, the Geum River sites seem to have been active from sometime after 475 to around 500.

Goguryeo Tombs of Southern Korea

Tomb Location and Arrangement

At present, a total of 35 Goguryeo tombs have been identified in southern Korea. They have been found in the vicinity of large rivers (Imjin-Hantan Rivers, the upper reaches of the Bukhan River, and the upper reaches of the Namhan River), as well as at several inland locations (Seongnam, Yongin, Hwaseong). The inland tombs are found on flatland sites situated near rivers. Therefore, riverside locations can be identified as a common feature of these Goguryeo tombs. The tombs are found in isolation or in small groups of two to three. However, a single row of five tombs was discovered at the Dujeong-ri burial ground in Chungju, while the Gangnae-ri burial ground in Yeoncheon included a total of nine tombs, comprising three rows of three tombs each. Goguryeo tombs are also characterized by their placement on low flatlands and their construction in rows. Although only a limited number of tombs were constructed over a large area in southern Korea, the present evidence indicates that the tombs were located and arranged in regular patterns (Fig. 13).

Tomb Structure and Construction Method

Goguryeo tombs were covered with square earthen mounds (Fig. 14). The burial chamber was located either above ground or, more frequently, at a semi-subterranean level. The former type was built directly upon a prepared ground surface, but in some cases, an L-shaped pit was cut into an inclined ground surface prior to tomb construction. If the base soil was uneven, a fine clay mixture would be used to smooth it out. For the semi-subterranean burial chambers, stone walls were raised in the burial pit, and the space between the earth and the stone was filled with clay (Fig. 15).

The types of stones that were used differed according to the size and shape of the burial chamber, but flat stone slabs were generally used as the basic building material. The walls of the burial chamber were typically built by stacking rectangular slabs, with smaller stones used to fill the space between the slabs. Some of the chambers also had plastered walls.

It was not always possible to conclusively identify structural elements of the tombs, but in some cases ceilings with parallel triangular corbels were confirmed (section highlighted in Fig. 15). Also known as a “laternendecke” or “lantern” ceiling, this structure was formed by stacking stone slabs atop the walls of the burial chamber, and then placing a large stone slab at each corner of the wall, forming four quadrants that constituted the ceiling. A passageway led to the burial chamber, which generally connected to the short wall on the right side of the burial chamber. The passageway had a flat ceiling comprising several stone slabs, and the section where the passageway met the walls of the burial chamber was covered with a large, rectangular piece of worked stone, which acted as a lintel for the doorway.

The f loors of the tombs were often specially treated with either plaster or fire; in a few instances, the tomb floors were either partially or entirely paved with stones or slabs of cut stone. Some of the burial chambers contained stone platforms onto which the coffin of the deceased would have been placed, but most of the burial chambers with stone floors did not have a platform. The platforms were usually positioned on the left side of the burial chamber, but a tomb from the Cheojeon-ri burial ground was found to have two platforms, one on each side of the burial chamber. The platforms, which generally were around ten cm in height, were made by stacking either river stones or cut stones.

In terms of dimensions, Goguryeo tombs of southern Korea can be divided into those with small burial chambers (length of long wall less than 2.2 m) and medium burial chambers (length of long wall greater than 2.2 m). In terms of the floor plan, the burial chambers are typically rectangular structures; some are longer than others, with the long walls more than 1.6 times longer than the short walls (Fig. 16).

Artifacts from the Tombs

The Goguryeo tombs of southern Korea have not yielded many artifacts; moreover, the artifacts that have been unearthed do not show a great deal of variety. The most commonly found artifacts are items associated with the burial itself, such as coffin nails and rings. Other artifacts include pottery, jewelry, and other articles of personal adornment (e.g., gold and glass beads, silver bracelets, silver rings), and such iron implements as hairpins, knives, and rings.

As mentioned, coffin nails represent the majority of the artifacts, with a total of 189 nails recovered from nine tombs. Some of the nails have round heads, some have square heads, and some are L-shaped, with no distinguishable head. The roundheaded nails are most common, while the square-headed and headless nails are few in number. Coffin rings have also been identified at Gangnae-ri Tombs 2, 4, 7, 8 and Bojeong-ri Tombs 1, 2. Each coffin ring consists of a base plate, connecting ring, and ring-shaped handle. The base plates of the coffin rings from the Bojeong-ri burial ground are circular, but those from the Gangnae-ri burial ground are flower-shaped and more decorative.

Seven pottery vessels have been found in the tombs, belonging to four functional types: bottle, deep bowl, globular jar, and jar with elongated body. Four of the vessels are globular jars; each of the other three types is represented by a single artifact. In general, globular jars can be classified into various subtypes, while those found in the Goguryeo tombs represent just two types. Three of the discovered jars are C-type (with a long globular body and short protruding neck), while the fourth is B-type (with a slightly flattened body and short protruding neck). The B-type globular jar, found in Dujeong-ri Tomb 2, is similar to one from Gosan-dong Tomb 11 in Pyeongyang. However, the former has a slightly longer body and is widest at the center of the body, which would date it to the mid-fifth century, which is slightly earlier than the latter (Fig. 17).

The C-type globular jars from Bojeong-dong Tomb 2 and Cheonggye-ri Tomb Chamber 1 are almost identical to those from Mongchon Fortress. The two former jars were decorated with the same pattern as many of the globular jars from Mongchon Fortress. Thus, based on the chronological scheme established for Mongchon Fortress, the jars can be dated to the late fifth century (c. 475 - 500), the same as the Mongchon jars. Another globular jar was found in Gangnae-ri Tomb 8, but it differs from the other two C-type globular jars in that the widest point of its body is located at the center of the vessel. Based on this difference, the C-type jar from Gangnae-ri is earlier than the other two, and can be dated to the mid-fifth century.

Tombs 2 and 8 of the Gangnae-ri burial ground yielded silver bracelets and associated gold and glass beads. A silver ring was also found at Dujeong-ri Tomb 4. The gold beads were hollow and shaped like abacus beads, with holes through the center or sides, so that they could be threaded or suspended (Fig. 18).

Chronology of the Goguryeo Tombs of Southern Korea

The Goguryeo tombs of southern Korea can be classified into small- and medium-sized tombs. They can also be classified into rectangular and elongated rectangular tombs, with the latter having long walls that are more than 1.6 times longer than the short walls. As can be seen in Figure 14, the nine tombs from the Gangnae-ri burial ground and the five tombs from the Dujeong-ri burial ground all belong to the elongated rectangular tomb type, as does Bangdong-ri Tomb 2. Of these elongated rectangular tombs, Dujeong-ri Tomb 2 and Gangnae-ri Tomb 8 have yielded C-type globular jars that can be dated, based on their shape, to the mid-fifth century.

On the other hand, Bojeong-dong Tomb 2 and Cheongae-ri Tomb 1, representing the rectangular tomb type, have yielded C-type globular jars dating to the late fifth century (Fig. 12). It is also known that the burial chamber of Goguryeo stone tombs with horizontal entrances, which were initially rectangular, generally became more square-shaped over time. Based on this knowledge and the differences in the grave goods, the tombs with elongated rectangular burial chambers can be dated to the mid-fifth century, and those with rectangular burial chambers can be dated to the late fifth century.

Various elements of the burial process seem to have been closely related, including the shape of the burial chamber, floor treatment, and stone plat-forms. Specifically, elongated rectangular burial chambers frequently had treated floors, but generally did not have stone platforms. Rectangular burial chambers, on the other hand, usually had stone platforms, but not treated floors. The type of floor treatment also differed according to the shape of the burial chamber. In all of the elongated rectangular burial chambers, the floors were treated with fire, but in the few instances of rectangular burial chambers with treated floors, the methods of the treatment varied. To summarize, in the mid-fifth century, coffins were often placed directly on the burial chamber floor, which had been treated with fire; in the late fifth century, stone platforms were used and the deceased was often placed directly (i.e., without a coffin) onto the stone platform.

Southern Expansion of Goguryeo in the Fifth to Sixth Century

According to such historical records as Samguk Sagi (History of the Three Kingdoms), the Goguryeo army advanced into the Chunggu region via the upper reaches of the Bukhan and Namhan Rivers in the late fourth century. In 396, King Gwanggaeto the Great (374–413; r. 391–413) attacked the Baekje capital of Hanseong, which resulted in the surrender of King Ashin. It is said that King Gwanggaeto the Great then returned home victorious, having annexed 52 walled towns and 700 villages north of the Han River. In 475, Goguryeo’s King Jangsu attacked Hanseong once again, killing King Gaero and forcing Baekje to move its capital south to Ungjin. According to Samguk Sagi, King Jangsu and the Goguryeo army returned home after Hanseong fell. Because the historical situation was not clearly recorded, there has been much debate over who controlled the Han River region, where the Baekje capital was originally located, after 475.

Fortunately, the discovery of Goguryeo remains at Mongchon Fortress has shed some light on this matter. The archaeological evidence clearly shows that some Goguryeo soldiers remained at Mongchon Fortress after King Jangsu returned home with his army. Furthermore, sites such as Daemo Mountain Fortress, Namseonggol Mountain Fortress, and the site in Wolpyeong-dong all date to the late fifth century—similarly to Mongchon Fortress—which suggests that Goguryeo continued its southern expansion into the Geum River region, with Mongchon Fortress as its base. In addition, the irregular shape of the ground-level building at Mongchon Fortress, along with the discovery of ceramic ritual vessels, suggests that the commanding officer at the site was a person of considerable rank. Based on such evidence, the fortress seems to have been a central component of the state’s southern expansion policy. Moreover, excavations at Namseonggol Mountain Fortress indicate that it also may have functioned as a base fortress, given its scale and the contents of the site. Thus far, excavations have yet to be carried out at Daemo Mountain Fortress, so it is not known whether it also might have served a similar function. Therefore, Goguryeo’s attempts to expand its borders south of the Han River appear to have been carried out from these base fortresses.

Even though the Goguryeo tombs of southern Korea are distributed over a wide area, they demonstrate a high degree of standardization in terms of their structure. The artifacts found within the tombs indicate that they were constructed by a Goguryeo population over a relatively short period of time, from the mid- to the late fifth century. Thus far, only a few tombs have yielded artifacts that can provide information about the deceased; Gangnae-ri Tombs 2 and 8 contained gold beads, silver bracelets, and glass beads; a silver ring was found at Dujeong-ri Tomb 4. The tombs containing these accessories are relatively large in size, suggesting that individuals of high status were buried in the Goguryeo tombs of southern Korea.

In addition to fortifed sites and tombs, Goguryeo settlements and other sites yielding Goguryeo pottery have also recently been discovered. Most such sites were later reused by Silla populations, however, so it is difficult to identify with certitude archaeo-logical features or cultural strata that can be clearly assigned to Goguryeo communities. Even so, Goguryeo pottery is present at these sites, and settlement sites containing similarly shaped and decorated vessels can be dated to the late fifth century (Fig. 19).

Notably, these settlement sites have a characteristic pattern of distribution: the Udu-dong site in Chuncheon is located near the Mancheon-ri burial ground; the sites of Cheoljeong-ri and Yeongnae-ri in Hongcheon are located near the Cheoljeong-ri and Yeongnae-ri burial grounds; the Tappyeong-ri site in Chungju is located near both the Dujeong-ri burial ground and the Jungwon Goguryeo Monument; the Mabuk-dong site in Yongin is located near the Bojeong-ri burial ground. In addition, a great number of fortification sites have been found in the vicinity of the Sindap-ri and Gangnae-ri burial grounds, along with the Joowol-ri site in Paju. Based on this distribution pattern, the tombs at these burial grounds seem likely to have contained the remains of Goguryeo people who lived in the nearby settlements or fortification sites. Therefore, it seems reasonable to assume that the individuals buried in the Goguryeo tombs were not high-ranking officers who had fallen in battle, but elite members of Goguryeo communities that had long been established in the region. In conjunction with the distribution of Goguryeo fortification sites, this interpretation indicates that, although King Jangsu returned to Pyeongyang Fortress in 475 after attacking Hanseong, Goguryeo maintained control over the captured areas.

How far did Goguryeo expand its southern boundary following the fall of Hanseong, and how was this southern expansion strategy carried out? Archaeological remains from Daemo Mountain Fortress (in Cheongwon) and the Wolpyeong-dong site (in Daejeon) demonstrate that the Goguryeo territory reached its largest point in the fifth century. The southern boundary fluctuated over time, but extended as far south as the Daejeon area of the Geum River region, which was deep into Baekje territory.

Goguryeo’s method of controlling their annexed regions south of the Han River also has been the subject of much debate. The archaeological evidence suggests that the territory acquired by King Jangsu was governed directly, a strategy that contrasts with the earlier methods employed by King Gwanggaeto the Great. As for the detailed methods of governance, several scenarios can be proposed. The territory may have been reorganized as a habu (下部), an administrative unit that is mentioned in the Jungwon Goguryeo Monument. Although the traditional regional administrative system of Goguryeo (i.e., the gun-hyeon 郡縣 system) may not have been applied to this territory, the habu may have also been further divided into smaller units that were referred to as gun and hyeon, with the fortress acting as the administrative center for these regional units (Yi Hoyeong 1984, 5-8). Notably, the Han River region is also known to have been a Goguryeo gun at the time that it was reclaimed by Baekje forces in 551 (No Taedon 2005, 185-6).

Then what happened to Hanseong after it fell to Goguryeo forces? It has been suggested that the forts of Mt. Acha and its environs were constructed to defend South Pyeongyang (Nampyeongyang), which was located in the area of the Jungnang River. These facilities are thought to have been established in relation to King Munjamyeong’s southern expedition of 495 (Choe Jangyeol 2001). It is believed that South Pyeongyang — which had been under the administrative control of Jangsu Mountain Fortress, located in Sinwon-gun, Hwanghae Province, until the midfourth century—was relocated to the Han River region after 475 (Son Yeongjong 1990, 175-8).

According to this view, Goguryeo stationed its forces at Mongchon Fortress after the fall of Hanseong in 475, but continued to refer to the Baekje capital as “Hanseong.” Then, after 495, South Pyeongyang was established on the flatlands immediately to the north of the Han River. This scenario coincides with the author’s interpretation that the Goguryeo forces stationed at Mongchon Fortress after 475 were later withdrawn to the forts of Mt. Acha on the northern banks of the Han River.

Evidence indicates that local officials were sent to the Han River region in order to implement Goguryeo’s territorial control over the region. The gun units were administered by susa (守事), who were officers of the daehyeong (大兄) rank in the Goguryeo state. As the term “susa” also appears in the text of the Jungwon Goguryeo Monument, it seems likely that the Han River region comprised an administrative unit similar to the gun (No Taedon 2005, 187), which in turn suggests the presence of a local official, such as a susa. As yet, there is little direct evidence for this possibility, but the discovery at Mt. Acha Fort 4 of a pottery piece bearing the inscription of “hubudo○hyeong” (後卩都○兄) may shed some light on the matter (Fig. 20, left). In this inscription, “hubu” (後卩) can be taken to mean “hubu” (後部, one of the five centrally ruled districts of Goguryeo) and “do○hyeong” (都○兄) seems to be the name of a person or rank. A similar example can be found in a stone inscription from Pyeongyang Fortress, reading “丙戌十二月中漢城下後卩小兄文達節自此西北行涉之” (Fig. 20, right). The inscription dates to the byeong-sul year, or 566, so it postdates the example from Mt. Acha Fort 4. As the two inscriptions are relatively close chronologically, and given that Hanseong in the Han River region was relocated to the Sinwon region of Hwanghae Province in 551 (Son Yeongjong 1990, 177), the hubu of the Mt. Acha Fort 4 inscription can be taken to mean the hubu district of Hanseong. If that is the case, then it would be reasonable to assume that the Han River region at the time was also divided into several districts, as was the capital region of Goguryeo. The Mt. Acha Fort 4 inscription does not contain any rank names, so it is difficult to know the precise rank of the administrative officer that was dispatched. However, it is highly likely that officers of various ranks were dispatched to the region.

Conclusion

At present, the earliest Goguryeo artifact to have been unearthed in southern Korea is the globular jar from the site of Juwol-ri in Paju, which dates to the late fourth or very early fifth century. Stone chamber tombs with horizontal entrances and elongated rectangular burial chambers appear from the mid-fifth century onward. The construction of these tombs (e.g., from the Gangnae-ri and Dujeong-ri burial grounds or Bangdong-ri Tomb 2) can be understood in relation to Goguryheo’s advancement into and annexation of the Chungju region, via the upper reaches of the Bukhan and Namhan Rivers, which took place in the late fourth century. On the other hand, the appearance of stone chamber tombs with horizontal entrances and rectangular chambers can be understood in relation to the advancement into and annexation of the areas of Jinchon, Cheongwon, and Daejeon by Goguryeo forces stationed at Mongchon Fortress, following the fall of Hanseong in 475. The fact that Goguryeo settlements have regularly been discovered in the vicinity of the tombs indicates that Goguryeo intensively and continuously maintained control over the captured territories for a substantial period of time. Archaeological remains of Goguryeo activity at Mongchon Fortress, Daemo Mountain Fortress, Namseonggol Mountain Fortress, the Wolpyeong-dong site, Eundae-ri Mountain Fortress, and Dangpo Fortress all date to the late fifth century, and can also be associated with Goguryeo’s attempts to maintain control over the Jinchon, Cheongwon and Daejeon areas. Finally, in the sixth century, Goguryeo forts came to be established on Mt. Acha and its environs, north of the Han River, and most of the forts of the Yangju Basin and the Imjin-Hantan River region also appear to date to this period.