[citation needed] General Yi Sŏng-gye, who was ordered to attack the Ming to regain Liaodong retreated from Wihwado and overthrew the Goryeo and established the Joseon dynasty.

Taejo's father, Wang Yung (later posthumously given the temple name of Sejo of Goryeo), along with many local clans, quickly surrendered to Kung Ye.

[13] He met Later Baekje forces and suffered a disastrous defeat, losing most of his army, including his generals Kim Nak and Sin Sung-gyŏm, the very same man who crowned Wang as a king.

[21] He then sent Ha Kong-jin and Go Yeong-gi to sue for peace,[32] with a promise that he would pay homage in person to the Liao emperor, and the Khitans, who were sustaining attacks by the regrouped Korean army and disrupted supply lines, accepted and began their withdrawal.

[35][page needed][36] Afterward, Hyeonjong did not fulfill his promise to pay homage in person to the Liao emperor, and when demanded to cede the Six Garrison Settlements, he refused.

[21][29] The Liao army was immediately ambushed and suffered heavy casualties: the Goryeo commander Kang Kam-ch'an had dammed a large tributary of the Yalu River and released the water on the unsuspecting Khitan soldiers, who were then charged by 12,000 elite cavalry.

[30] The History of Liao claims that Hyeonjong "surrendered" and Shengzong "pardoned" him, but according to Hans Bielenstein, "[s]horn of its dynastic language, this means no more than that the two states concluded peace as equal partners (formalized in 1022)".

[40] Kaesong was rebuilt, grander than before,[41] and, from 1033 to 1044, the Cheolli Jangseong, a wall stretching from the mouth of the Yalu River to the east coast of the Korean Peninsula, was built for defense against future invasions.

Led by prominent generals such as Yun Kwan and Ch'ŏk Chun-gyŏng, the well-trained Byeolmuban (別武班; "Special Warfare Army") of approximately 250,000[50][51] men initially succeeded in ravaging Jurchen territories and building the strategic "Nine Fortresses" (동북 9성, 東北九城) of which exact locations are still topics of debate.

[58] In addition, under the reign of King Uijong, military officers were prohibited from entering the Security Council, and even at times of state emergency, they were not allowed to assume commands.

[59] After political chaos, Uijong started to enjoy traveling to local temples and studying sutra, while a large group of civilian officers almost always accompanied him.

[68] What was different from former military leaders was the active involvement of scholars in Ch'oe's control, notably Prime Minister Yi Kyu-bo, who was a Confucian scholar-official.

[68] Although the House of Ch'oe established strong private individuals loyal to it, continuous invasion by the Mongols ravaged the whole land, resulting in a weakened defense ability, and the power of the military regime waned.

There were six significant campaigns: 1231, 1232, 1235, 1238, 1247, and 1253; between 1253 and 1258, the Mongols under Möngke Khan's general Jalairtai Qorchi launched four devastating invasions against Korea at tremendous cost to civilian lives throughout the Korean peninsula.

In March 1258, the dictator Ch'oe Ŭi was assassinated by Kim Chun after which authority was restored to the monarchy and peace was made with the Mongols; however, power struggles continued in the court, and military rule did not end until 1270.

The Eastern Route Army arrived at Hakata Bay on June 23, and decided to proceed with the invasion without waiting for the larger Southern force which had still not left China.

[84] Gongmin regained Goryeo's Independence in the mid 14th century, and afterward Generals Ch'oe Yŏng and Yi Sŏng-gye rose to prominence with victories over invading Red Turban armies from the north and Wokou marauders from the south.

He used the conflict to reform the Korean government, abolish Mongolian military outposts, purge pro-Yuan sentiments, and regain lost northern territories such as Liaoyang.

[88][89] Chŏng Mong-ju was dispatched to Japan to deal with the problem, and during his visit Kyushu governor Imagawa Sadayo suppressed the early wokou, later returning their captured property and people to Korea.

Although the functions of Jungbang in the early Goryeo period are unclear, it was a gathering of the highest-ranking military officials directly under the top civil offices, thus having significant potential for wielding power.

In 936 (19th year of Taejo), when waging the unification war against Sin Geom's army of Post Baekje, Goryeo's military comprised Junggun, Jwagang, and Ugang.

The organization gradually collapsed as the war persisted for an extended period, and it became systematically challenging to support them, Juhyeon-gun disappeared during the latter days of the battle against the Mongolians.

[11] In the early Goryeo period, the pirates from the Eastern Jurchens (Dong Yeojin, 동여진; 東女眞), who frequently invaded the East Coastal Region, were defeated by the naval forces in the Seonbyeongdo department during the winter season.

[11] During Yejong's reign, General Yun-Gwan led 2,600 naval forces from the Seonbyeongdo department in a winter's conquest against the Jurchens as they were active in Dorinpo County.

In 1275 (the 15th year of King Wonjong), they invaded Japan with the Mongols, consisting of 5,300 Goryeo soldiers, 900 Byeongseon ships transporting carriers (chogong, 초공; 梢工) of great millets (Susu, 수수; 蜀黍) participated in the war.

General Jeong Ji, who insisted on fostering naval forces, became Marshal of Haedo and defeated Japanese ships in Jinpo County, Gunsan Island, etc.

[101] In 1010, Goryeo shipbuilders developed the Gwaseon; the ship was designed to sail fast and ram and destroy Japanese and Jurchen pirate vessels that were attacking Korean coastal cities with spears attached to the bow.

[106] Following the collapse of United Silla in the 10th century and its takeover by Goryeo, the warfare style more familiar to the Central and Northern parts of Korea, along with the use of lighter armor inspired by the Song dynasty, took over.

The trend shifted towards armor that made units mobile and responsive to a conflict with nomadic Mongolic or semi-nomadic and sedentary Tungusic tribes to the North.

[116] Local production did not begin until Ch'oe Mu-sŏn, a minor military official, learned potassium nitrate purification methods from a visiting Chinese saltpeter merchant.