After extending its borders northward, Koryo came into contact and conflict with the Manchurian Chitan Dynasty. In wars, lasting from 993 AD until 1018 AD, Koryo was able to maintain its position, until the Chitan Manchurians invaded Koryo in 1011 AD. In 1022 AD, Koryo gained a definitive peace, by accepting Chitan suzerainty.
The 11th century was marked by a stable government, many Buddhism inspired achievements in scholarship and art, and a distinctive ceramics industry. Then in 1170 AD, a military coup seized control of the country and, by the end of the twelfth century, the Cho family ruled Korea and suppressed Buddhism. The Cho armies fought the Mongolians but they were soon defeated by the sheer numbers of Mongol troops. Internal political conflict and external pressures from the Manchurian Jurchen Dynasty led to government instability. In 1231 AD, Mongols, under the leadership of Kublai Khan (who was greatly civilized by Confucianism), invaded Korea. In 1258 AD, the Cho regime was deposed and the Koryo government was returned to control, under the guidance of the Mongols.
The Mongols allied themselves with the Koryo ruling house by marriage and established a rule that lasted a hundred years. Koryo became a small fragment of the vast Mongol Empire was a full-fledged participant in the Mongol adventure of conquest. Koryo became the launching ground for Mongols attacks against Japan. Mogols forced Koryo to build two huge fleets of ships for an invasion of Japan; however, the invasion was unsuccessful. Thwarted by heavy storms which the Japanese called "divine wind" (kamikaze), the fleets were lost and Mongol power began to wane. The result was more war with large armies struggling to break the yoke of Mongol rule all over Central Asia and Korea. With Mongol power weakened, the Japanese stepped up their harassment of Korea's coastal areas using organized pirate raids. Exhausted by centuries of invasion and a hundred years of Mongol domination, Koryo's government and social structures gradually disintegrated. In 1356 AD, Koryo revolted against Mongolian rule, which brought another period of disorder to the Korean Peninsula.