Exploration and Analysis on the Historical Remains of Wooden Fence in Koguryo Mountain City

The mountain city is the one that is built as a kind of fortifications in the mountains by Koguryo people. This kind of city is widely distributed in the region of China’s Liaoning Province, Jilin Province and the northern part of Korean peninsula. Currently the Koguryo mountain cities seen in China are mostly stone-built and earth-built, and some are stone-and-earth mixed construction. This is because its regime’s early land is located in the mountains, and the use of stone is a native aboriginal tradition, but the later occupy is the plains, so the choice of building material became the earth according to local conditions. Recently, the author has found that there are some remains of the wooden fence in some small mountain cities, whose defense system are built by contacting the stone with the wooden fence, during the survey on the mountain city in Liaoning Province. The wooden fence should be an important part of the fortifications of the Koguryo mountain cities, and the cave stone relics previously discovered should also be related to this.


Introduction
The mountain city is a precious material cultural heritages of Koguryo nation, which has a necessary relationship with its own historical and cultural characteristics. Because the fighting has been frequent throughout the history of the Koguryo regime, the Koguryo people used the mountain city as an important means of defense against foreign enemies. Within the territory of China's Liaoning and Jilin province and the northern region of the Korean Peninsula, a large number of mountain cities are built to changing in terms of location, wall-building methods, stone processing. The study of these related issues is of great significance to the study of the history and culture of Koguryo. However, due to the limitation of archeological data, the research on the construction method of the mountain city mainly focuses on the construction methods of stone building, earth building and earth-rock mixed building.
In recent years, with the increase of the archeological data in the Korean Peninsula, the research on the wooden fence which works as a part of the fortifications has gradually drawn the attention of relevant scholars. However, the relevant material of the wooden fence in China is very limited, which makes the related research restricted. Recently, during the survey on the mountain city in Liaoning Province, the author found some remains of wooden fence in some of the small mountain cities, whose defense system are built by contacting the stone with the wooden fence, the wooden fence should be an important part of the fortifications of the Koguryo mountain city, and the cave stone relics previously discovered should also be related to this.

Heyang Temple Mountain City
Heyang temple mountain city is located in a corn-shaped dwarf mountain, two kilometers away from northwest of Zhengtun village, Gaizhou. Its altitude is 100 meters and the mountain is relatively flat.
The mountain city is high in the north, low in the south, and the flat is slightly rounded square. The city walls' construction is combined with two ways of low stone walls and stone walls with low stone. The remains of stone column is located in the middle and north section of the western wall of the mountain city.
Based on different ways of building the western wall can be divided into three sections: The first section is the southern part of the western wall. It is an about 220-meter long stone wall, and the mountain is slightly steep and rises step by step. The mountain city built the inner and outer wall by the local processed stone which was shaped into a size of about 20cm × 30cm, and filled gravel in the middle of the wall for reinforcement. This is the typical city wall construction style in the late Koguryo regime, and it's about a 110cm-120cm width. The existing part is only about half a meter high, and part of the wall remains only a layer of stone, less than 30cm high.
The second section is the middle part of the western wall. It is a large stone wall base, nearly 90-meter long. About 200 meters up along the west wall, the mountain slows down, and the wall body stands directly on the mountain in the form of simple processed or unprocessed large stones. Those stones are 55cm-58cm high and 47cm-57cm long, and formed into two rows of low stone wall base inside and outside. The width between inner and outer stones of the wall is 42cm-44cm, and did not fill soil between them.
The third section is the northern part of the western wall nearly 100-meter long. This part of the wall is near the top of the mountain, located in the spread and gentle ridge near the west door, and the www.scholink.org/ojs/index.php/wjssr difference of height between the ridges is small. From the north to the south the wall is about 110-meter long, and the stone wall base was made up by the simple processed small stones, large unprocessed stones and huge stones. The small stones are about 40cm-55cm high, 53cm-37cm long. The width between inner and outer stone row is about 40cm-44cm. The west door of the wall connects the outside ridge of the valley, for the mountain is flat and open, and the defense pressure is great. The Koguryo chose large or huge stone to construct the defense system. The large stones are 71cm-110cm high and 110cm-120 cm long, and the width between the inner and outer wall is 50cm-55cm, and those huge stones are nearly 2-meter high and directly cut out 32cm-40cm base groove to distinguish the inner and outer wall.

East Fenying Mountain City
The construction style of Heyang Temple Mountain City's western wall is not the isolated example of the Koguryo mountain city, the East Fenying mountain city is also adopted the similar construction method.
East Fenying mountain city located in a mountain about 160 meters above sea level is in the east of Fenying village, Yangyun town, Gaizhou City. Its southern wall is built by the local stones and two kinds of masonry methods are adopted. It is located on the top of the ridge and more than 400-meter long. Due to the steep mountain near the door, the wall from the west valley mouth towards more than 200 meters south, was built by the simple processed stones as inner and outer wall, and filled gravel and small stones in the middle. Now the remains are 30cm-50cm high and 100cm-110cm wide.
As the ridge gradually becomes widening and flat, and the defensive pressure eased with being away from the gate, the construction of the southern wall becomes a similar way with the second part of the western wall of Heyang temple mountain city. The inner and outer walls are respectively divided into two columns by natural large stones about 60cm in height and 8cm-100cm in length. The distance between the two columns is 50cm-55cm, and there is no filled wall core between the two columns of stones inside and outside. The height of the native stones is the height of the wall base. In addition, Tangpu city in the Linjin River Basin, and the second fort of Yeoncheon-gun in gyeonggi, also confirmed the remains of the wooden fence.

The Relationship between the Low Stone Wall and the Stone Cave
It can be seen that the defense system with the combination of the stone wall and wooden fence is

Conclusion
From the way the city is constructed, Heyang temple mountain city and East Fenying mountain city should be the small and medium-sized mountain towns built in the artery between south and north in the west bank of the Liaodong peninsula in the late period of koguryo. military positions. Only a few soldiers were stationed in this kind of mountain city which acts as the stronghold and fort during wartime at ordinary times. Koguryo in such a region built the wooden fence walls without spending much time and energy, which clearly fitted its military need better.
From the stone caves popular in early and late period on the top of the mountain city wall built with rocks to the pillar holes on the top of the small mountain city in Hankang River basin in the middle of the regime, late to the stone columns at the top of the mountain city located in Liaodong Peninsula plains, although the shape of infrastructures had been changing, the defense system in which the wooden fence and walls are belt together had always been used. It should be seen that Koguryo people chose to build palings at that special time period and region. It is an important part of Koguryo mountain cities to use the respective defense systems timely and properly according to the natural environment and the defense needs.