This paper examines the transitional stages and their characteristics of the fortification of the Goryeo Dynasty in the war against the Mongols, based on the archeological discoveries of the fortresses which were used in the offensive and defensive battles during the war. Through this research that was essential in supplementing the shortage of historical document of that age, I intend to find how the advent of the rugged mountain protective fortress had influenced the history of the Korean fortress.

In the 2nd chapter, the castle of Gaegyeong, the capital of Goryeo, is firstly examined as the representative fortification model of the pro-Mongol's invasion. Then, based on the postal road system, the interconnectedness between the Goryeo's North Advancement Policy and their fortification is analysed. I also examine the process of the construction of Cheonrijangseong(One thousand ri wall) and the state of forts which were built in the antagonistic relationships to Tungus or Jurchen. Through the review on the castle constriction process of Pyeongtaek area and the change of administration offices, I search out the state of the province and city castles in the early Goryeo period. In addition, I verify the aspects of the offensive and defensive battle before the period of the war against the Mongols, by way of the review of the battles at the Seogyeong castle during the rebellion of Myocheong. Also, I arrange about the catapult and cross bow, which were used in the battle of the Seogyeong castle, through the research of 『the Book of Military Tactics』. It was revealed that weapons and tactics which were used in the battle of the Seogyeong castle had been maintained for 100 years until the period of the war against the Mongols.

The 3rd chapter shows the aspect of the war between Goryeo and Mongols. I search the siege tactics of Mongol army. That research was based on the recent researches and the records of Cho Kong's『Secret record of Mongol and Tatar』and Peng Daea and Seo Jeong's『Outline story of Tatar』. These included the records of spying of the military experts of North Song in 1230’s for the future emergency. Through these records, I can guess that Mongol army used the raid and surround tactics to siege the Goryeo fortress and through the records of the fortress offence and defence battle during the period of the 6 times war against the Mongols. I analyses the fortress seize tactics of Mongol and the defence tactics of Goryeo. Based on these findings I finds that the Goryeo's Ganghwa-do Island government changed its protect tactics into the ways of island and mountain fortress defending tactics. Ganghwa-do Island government dispatched the mountain fortress guard officer to the inland fortresses to protect the invasion of Mongol. However, after the 5th war, protective fortresses changed from the province and city defence to the mountain and I study the background and process of changing.

In the Chapter 4, attempts are made to divide the fortresses which were lasted for 40 years against Mongol's invasion into the Ganghwa and capital fortress (Jindo Yongjang fortress, Jeju island Hangpaduri fortress), and inland fortresses. Each fortress is examined through the conditions of location, structure and remains. Based on this, I can grasp the general operation and castle construction system of the protective fortress in the period of the war against the Mongols. Furthermore, I conclude how they were operated in the fighting with Red scarfs and Japanese pirate raiders and be developed for the territory defense policy in the Early Choseon dynasty. Lastly, I search the change of the fortress battle in the war against the Mongols. However, I cannot find any big change of the offence and seize tactics, and weapons of Goryeo and Mongol each side. Since the 5th war which Mongol invaded early with pro-Mongol power, Mongols stayed for over a year to pressure the Ganghwa Island government. So, Ganghwa Island government reinforcing the defence line from Chunju to Myeongju Province built protective fortresses on the rugged mountains.

The main point that this paper concentrate is to introduce the changing of protective fortress of the island and inland.
Protective fortress of the island was followed with the capital form fortress. Firstly, fortress system shows that Gaegyeong is divided in 3 parts; palace – capital – outer fortress. Ganghwa capital is triple fortress; palace – middle fortress – outline fortress. Jindo Yongjang fortress is double building; inside fortress – outer fortress. Jeju island Handpaduri fortress is 3 parts fortress, fortress system of Gaegyeong; inside fortress – outer fortress – coastline long wall. The capital of Gaegyeong, middle fortress of Ganghwa and outer fortress of Jeju Hangpuduri is made in earth. Gangwha middle and Jeju Hangpaduri outer fortress were investigated archeologically. Building method of them, section building with frame and especially, in the case of Ganghwa middle fortress, space of width wood block were widen in 4~4.5m, shows the most improved castle construction system since the period of Three Kingdoms. Also, this construction was kept until the end of Goryeo and early Choseon. However, earth castle construction in the period of the war against the Mongols disappeared later and it changed to the inside reinforce system which add inside of the stone wall of city fortress.

With regard to the changes of protective fortress, there are the conditions of location and defence equipment. Mountain fortress of the period of the war against the Mongols were constructed as the forms of Gorobong-hyeong(Type of fortress running from hilltop in all directions) and Samobong-hyeong(Type of fortress located on the top of hill). The examples of Gorobong type are Gwangju Namhan mountain fortress, Anseong Jukju mountain fortress, Chuncheon Bongeu mountain fortress, Youngweol Jeongyang mountain fortress, Janghueng Suin mountain fortress, Jangseong Ipap mountain fortress and Damyang Keumseong mountain fortress. The examples of Samobong type are Sokcho Kwongeum fortress, Inche Hankye mountain fortress, Chuncheon Samak mountain fortress, Chungju Daelim mountain fortress, Chenliong mountain fortress, Jecheon Wolak mountain fortress, Goesan Mireuk mountain fortress and Sangju Geumdol fortress. These locations were chosen because they have the advantages not only to protect(prevention of the trooper’s attack, concentration of defence equipment and abundant supply of defence weapon, stone), but also expropriate civilians and secure enough source of a stream. They enshrined various facilities; protective and attachment facility, gate and gate defence equipment, watchtower and service facility expansion and reinforcement, beverage and warehouse reinforcement, religion facility to bind protective civilians.

Position and castle construction of protective fortress can be explained as follows:
① Gorobong and Samobong types were chosen on the rugged and high location.
② Scale was bigger then Three Kingdoms and sometimes enlarging the previous ones.
③ Water source was enough since one more valley is inside.
④ The high wall was not constructed in the rugged area with cliffs.
⑤ Easy access area like Kockbu enlarged the wall scale.
⑥ Mostly, it was made as low flat arrow fence, not the arrow position,
⑦ Most wall had the flaw for pillars.
⑧ Gate was build in the access way to the mountain fortress, but used gate defence equipment complexively.
⑨ They built the watchtower and supply route castle to fit in the configuration to observe and control the invasion of enemy. Especially, it is not for just suppling, but for observing and being opposed to the enemy’s attack.

After the transfer to the Ganghwa Island, the emerging of the protective mountain fortress has some important meanings. Firstly, defence position changed from the city to the mountain fortress. Next, government mainly chose the defence position. However, in spite of the changing of defence position, resistance against Mongols depended on the guerilla warfare of local community of all the country and defensive battle, which was based on the local civilian, commanded by the region officer. The role of central government were strengthened during the war while local community was impoverished and the self-defence capability were getting weakened.

However, protective fortress had been maintained as invasions of Hapdan(King Chungryeol 19th year, 1290) and Red scarfs (King Gongmin) and reactivated as a protective defence point. In the period of King U, Japanese pirate raiders invaded to the inland and thus government needed to refuge the civilians to the mountain fortress. So, in the 3rd year of King U(1377), they built the protective wall or the camp to guard the road between towns for engaging wanderers in farming and for constructing mountain fortress in county. July of 1377, government dispatched commanders to all the provinces to build the mountain fortress and the role of fortress changed to protect the invasion of the north to that of Japanese pirate raiders. The changing of protective sites continued until year 10 of King Taejong, Choseon. Then, the role of protective mountain fortress was reduced in early Choseon because of concentrating the building of the coast town castle, military camp and port. However, among the protective mountain fortress which were used during the war against the Mongols, several fortresses were carefully selected and operated because of their strategical significance after the Japanese Invasion to Korea in 1592 and the Manchu war in 1636.