After a century and a half of peaceful relations with its neighbors Korea suffered from a destructive series of invasions. The first, and most devastating, came from the Japanese. In Japan, a bloody struggle for power among feudal lords temporarily ended when a powerful warlord, Toyotomi Hideyoshi (1536–1598), unified the country. Hideyoshi then launched an invasion of Korea with the intention of using the peninsula as a base to conquer China. It is unclear if he was motivated by megalomania or a desire to direct the energies of warriors harmlessly abroad. Or perhaps the invasion of Korea was merely a continuation of his drive to extend his power, the next step after he had brought the autonomous domains of western Japan under his control. Hideyoshi assembled a quarter of a million men for what was probably the largest overseas invasion in history before the twentieth century. Korean officials received rumors of preparations for an invasion by 1591, but debated among themselves over the reality of the threat and only made some inadequate efforts to strengthen their defenses. When the initial contingent of 52,000 troops landed in Pusan on May 23, 1592 (by the solar calendar), they overran the coastal fortifications that were defended to the death by the local commander. The Japanese forces then advanced quickly up the peninsula. Their foot soldiers were armed and well trained in musketry, which they used to great effect. One unit of Japanese would fire volleys of muskets into the Korean forces, overwhelming them with musket power, while other units would attack with swords on the right and left flanks, decapitating as many as they could. Korean troops, who would defend themselves by massing together, were then slaughtered in great numbers. So effective were Japanese tactics that three weeks after the start of the invasion the Japanese captured Seoul and then pushed north.
The Choson court fled ahead of the enemy advance, abandoning the defense of the capital to slaves and commoners. Disgusted onlookers jeered and even threw stones at the royal entourage as it made its way to Uiju on the Chinese frontier. Slaves in Seoul took advantage of the chaos to burn palaces and offices and to destroy the registers that documented their status. After a pause for regrouping and supplying their forces, the Japanese under General Konishi Yukinaga captured P’yongyang on July 23. A second wing under General Kato Kiyomasa and General Nabeshima Naoshige advanced northeast to the Yalu and Tumen rivers. The Korean army disintegrated under this massive and well-organized invasion. In desperation the Koreans appealed to China for help. The Chinese, fearful of this new threat from the east, responded with assistance. Led by General Li Rusong, himself of Korean descent, the Ming forces entered in January 1593 and defeated Konishi in battle at P’yongyang in February. The Chinese then advanced south, but did so too fast and were halted. Then the war began to stalemate in a way similar to the later Korean War.
Unlike the Korean War where Koreans fought on both sides, Koreans were united in their resistance to Japan, and after a poor initial showing they resisted more effectively. Peasants often fiercely fought to defend their villages from these strange, dangerous outsiders. Local yangban, monks, and others formed resistance bands called uibyong (“righteous armies”). Among the more effective groups were ones led by Cho Hon in Ch’ungch’ong province in south-central Korea, Kwak Chae-u in the southeastern province of Kyongsang, and Kwon Yul in the southwestern province of Cholla. While most were defeated, they made the Japanese position difficult, and along with the pressure from the Chinese forces they forced Hideyoshi’s troops to withdraw to the southern coastal areas. Especially successful was Admiral Yi Sun-sin (1545–1598), who waged a naval campaign that destroyed hundreds of Japanese ships and made supplying and reinforcing Japanese troops costly. Yi came from a family of civil officials but chose to take the military rather than the civil examinations. He served as an officer along the northern frontier and later in Cholla. Alarmed by the reports of a possible invasion, he launched a last-minute shipbuilding effort. Yi experimented with new weapons and tactics. His most ingenious innovation was the kobukson (“turtle ship”), an ironclad ship designed to withstand Japanese cannon fire and to ram and sink its opponents’ vessels. These were the world’s first ironclad ships. The turtle ships proved to be highly effective. The first ship was completed just days before the Japanese landed. Yi with the help of his turtle ships led an effective naval campaign that prevented the Japanese from using the western coastal route to transport supplies and reinforcements to their army in the north of Korea, making resupplying their army in Korea from Japan hazardous.
With the war stalemated by 1594, the Chinese withdrew their forces to Manchuria and the Japanese to the southern coastal ports. A period of diplomacy began. Chinese diplomats came to Japan, but the negotiations revealed how little the Chinese and Japanese knew each other. The Chinese were willing to recognize Hideyoshi as the “king” of Japan and allow the Japanese to enter the Chinese tributary system. Hideyoshi in turn offered to form a marriage alliance with the Chinese emperor. Interestingly Hideyoshi offered to divide Korea, with the southern provinces coming under Japanese control and the northern parts under Chinese authority, thus roughly anticipating the division of Korea that the United States and the Soviet Union carried out three and half centuries later. Eventually negotiations broke down and the Japanese launched a second massive invasion in 1597. This time the Koreans and the Chinese under General Yang Hao were better prepared and limited the advance of the Japanese. Meanwhile, Yi Sun-sin, who had been removed from his post due to court intrigue, was given back his naval command. He scored a major victory at Myongnyang near Mokp’o. While chasing the retreating Japanese ships he was killed by a chance shot. Today he is remembered as a national hero and one of the world’s great naval geniuses. Suffering defeats at sea and stalemate on land, the Japanese generals withdrew their forces to Japan to participate in the jockeying for power that followed Hideyoshi’s death in late 1598.
The invasions, while a failure, were highly destructive, since the Japanese, like the Mongols earlier, used a scorched-earth policy to overcome resistance. As a result, they left behind a ruined countryside and a legacy of bitterness and fearfulness of the Japanese among Koreans. The viciousness of the conflict was symbolized by the 38,000 ears of Chinese and Korean forces sent back to Japan by military commanders as proof of their military successes. These were pickled and buried in Kyoto in the Mimizuka (Mound of Ears). The conflict provided later generations of Koreans with heroes from the fighting monks and peasants to Admiral Yi. It also led to a temporary and partial breakdown in the social order as slaves took advantage of the war to seek freedom. A court in desperate need of money sold official titles to commoners and even outcastes. These titles, however, did not become hereditary. While the Ming only intervened when it became clear that the Japanese were a threat to Chinese security, the invaluable assistance of China reinforced Korea’s tributary ties and its emotional connection with the Middle Kingdom. The conflict also brought Korean influence to Japan. Japanese forces brought back thousands of Korean captives. These included the scholar Kang Hang, who played a major role in introducing Neo-Confucian philosophy to that country, and potters whose rough-hewn Korean wares would influence Japanese ceramic traditions.
Hardly had Korea recovered from the Japanese invasions when it faced a new threat to the north with the rise of the Manchus. The Manchus were a Jurchen group who under their leader Nurhaci united the tribal peoples of what is now called Manchuria. In 1616, Nurhaci established the new state of Later Jin, a name derived from the Jurchen state of the twelfth century that conquered northern China. The Manchus then began attacking Chinese garrisons in the northeast. The Ming court called upon the Korean king for assistance. Realizing how vulnerable Korea was to a Manchu invasion, King Kwanghaegun (r. 1608–1623) sought to avoid becoming involved. When he sent forces to assist the Ming he secretly instructed his military commander to observe which way the battle was going, and when Manchu forces appeared to be emerging victorious the Koreans surrendered without fighting. Korea did not remain neutral for long. Kwanghaegun was overthrown in a power struggle led by some who were angered by his lack of support of the Ming, who had a generation earlier come to Choson’s rescue. The new group that placed Injo on the throne in 1619 pursued a pro-Ming, anti-Manchu policy.
Shortly afterward, Yi Kwal, a military officer who felt that his family had not been properly rewarded for his part in the coup, seized control of Seoul, forcing the court to flee. Yi Kwal was soon defeated. The new pro- Ming court then provoked a Manchu invasion of Korea in 1627. The court fled to its traditional refuge of Kanghwa Island while the Manchu forces looted P’yongyang. Bowing to reality the Koreans negotiated a tributary relationship with the Manchus, recognizing them as elder brothers and agreeing to make tribute payments of gold, cloth, and horses. The Korean court, however, still pro-Ming, broke off its tributary relations and allied itself again with the Ming in 1636. Nurhaci’s successor Abahai, who now styled himself emperor of the Qing dynasty, invaded Korea to secure his southern flank as he struggled to conquer China. Crossing the frozen Yalu River in the winter of 1636–1637, Manchu cavalry forces advanced quickly and captured Seoul. Injo (r. 1623–1649) retreated to a fortress south of the capital while members of the royal family and their entourage fled to the safety of Kanghwa. Injo and his forces, after holding out against a Manchu siege for weeks, surrendered when news arrived that the Manchus, succeeding where the Mongols had failed, had captured Kanghwa and with it the royal family. Injo then pledged his loyalty to the Manchu rulers. Seven years later the Manchus captured Beijing and the Qing dynasty (1644–1911) replaced the Ming.
For the next three and a half centuries Korea served as a tributary of the Qing dynasty. The Koreans, however, entered the relationship unwillingly, and hostility toward the Manchus remained strong. Some, such as the military commander Im Kyong-op (1594–1646), sought to renew hostilities. A number of Koreans were held hostage, including two princes, Sohyon and Pongnim; the latter became King Hyojong (r. 1649–1659). Hyojong upon becoming king prepared to support Ming loyalists who were fighting the Qing in China and planned for an attack. The Qing, however, eventually put down the loyalists and Koreans came to accept the reality of Manchu rule. The Koreans thereafter maintained correct if not enthusiastic relations with the new dynasty.