Imjin War (1592–1598): Japan's Invasions of Korea

The Imjin War was the series of two Japanese invasions of Korea launched by Toyotomi Hideyoshi in 1592 and 1597. Hideyoshi aimed to march through Korea and conquer Ming China, but Korean resistance on land and sea, together with a large Ming Chinese intervention, stopped him. The war, which ended only with Japan’s withdrawal after Hideyoshi’s death in 1598, was the largest conflict in East Asia in the sixteenth century and left much of Korea in ruins.

Background and causes

By 1590 Hideyoshi had completed the unification of Japan, ending a century of civil war with campaigns such as the Siege of Odawara. He commanded hundreds of thousands of experienced soldiers, many armed with arquebuses, firearms introduced by the Portuguese in 1543 and produced in large numbers in Japan.

Hideyoshi announced that he would conquer Ming China, and even spoke of going on to India. He demanded that Joseon Korea, a close tributary ally of the Ming, allow his armies to pass through. Historians debate his motives: personal ambition, a wish to reward his lords with new lands, and a desire to keep a large warrior class busy abroad all probably played a part.

Joseon Korea had enjoyed two centuries of relative peace and its army was poorly prepared. In 1590 King Seonjo sent envoys to Japan, but on their return they gave contradictory reports on whether an attack was likely, reflecting factional rivalry at court. Korea refused Hideyoshi’s demand.

The first invasion (1592–1593)

Hideyoshi built a great base at Nagoya in Hizen, northern Kyushu. In the spring of 1592 an army of about 158,000 men in nine divisions began crossing to Korea. The first division, under Konishi Yukinaga, landed at Busan on 23 May 1592 and stormed its fortress the same day; the nearby fortress of Dongnae fell soon after.

The Japanese advanced rapidly north along three routes. On 7 June 1592 the Korean general Sin Rip was defeated at Chungju, and King Seonjo fled his capital. Konishi’s troops entered Hanseong (modern Seoul) on 12 June, only twenty days after landing.

The speed of the advance owed much to Japanese experience. The invaders were veterans of decades of civil war and used massed arquebus fire, while Korean troops relied mainly on archery and on a mobilisation system that required local forces to gather and wait for commanders sent from the capital. Several Korean armies were defeated before they could fully assemble, and many soldiers deserted. Konishi went on to take Pyongyang in July, while Katō Kiyomasa advanced into the far north-east and captured two Korean princes.

War at sea

Korea’s salvation began at sea. Admiral Yi Sun-sin, commander of the left navy of Jeolla Province, had prepared his fleet of sturdy panokseon warships armed with cannon. Between June and October 1592 he won a series of victories along the southern coast, at Okpo, Sacheon, Dangpo and elsewhere, where he introduced the armoured “turtle ships” (geobukseon).

The most important was the Battle of Hansando on 14 August 1592, where Yi lured a Japanese fleet under Wakisaka Yasuharu into open water and destroyed most of it. These victories prevented Japan from supplying its armies by sea along the west coast, leaving its forces in the north short of food and reinforcements.

Righteous armies and the Ming intervention

On land, irregular volunteer forces known as “righteous armies” (uibyeong) harassed Japanese garrisons and supply lines. They were led by local scholars such as Gwak Jae-u and Go Gyeong-myeong and by Buddhist monks including Hyujeong (Seosan Daesa). In November 1592 the Korean garrison at Jinju under Kim Si-min beat off a major Japanese attack.

The Ming court, under the Wanli Emperor, decided it had to defend Korea to keep the war away from China. After a small force was defeated at Pyongyang in 1592, a much larger army under Li Rusong, usually estimated at 40,000–50,000 men, crossed the Yalu River and recaptured Pyongyang on 8 February 1593.

Li Rusong was then defeated at Byeokjegwan near Seoul on 27 February 1593, but on 14 March the Korean commander Gwon Yul repulsed a large Japanese assault on Haengju fortress. Short of supplies, the Japanese abandoned Hanseong in May 1593 and withdrew to a chain of fortresses (waeseong) on the south coast. In July 1593 they took revenge on Jinju, capturing the city and killing most of its defenders and inhabitants.

Negotiations, the second invasion and the end (1593–1598)

From 1593 to 1596 Japanese and Ming envoys negotiated while most fighting stopped. The main negotiators, Konishi Yukinaga and the Ming agent Shen Weijing, misrepresented each side’s terms to their own masters. In 1596 a Ming embassy in Osaka offered Hideyoshi investiture as “King of Japan” under the Ming emperor, which fell far short of his demands. He ordered a new invasion.

In 1597 about 140,000 Japanese troops were sent to Korea. Meanwhile Yi Sun-sin had been dismissed and arrested after court intrigues, and his successor Won Gyun led the Korean fleet to destruction at Chilcheollyang on 28 August 1597. The Japanese advanced into Jeolla Province, took Namwon in September and marched north, but were halted by Ming forces at Jiksan in October.

Restored to command with only a handful of ships, Yi Sun-sin won his most famous victory at the Battle of Myeongnyang on 26 October 1597. The Japanese pulled back to their coastal fortresses. In January and February 1598 a Ming and Korean army besieged Katō Kiyomasa in Ulsan; the starving garrison held out until relieved.

Toyotomi Hideyoshi died on 18 September 1598, and the regents who governed in the name of his young son ordered a withdrawal. As the Japanese tried to leave, Ming and Korean forces attacked their fortresses at Sacheon, Suncheon and Ulsan with mixed results. At the Battle of Noryang on 16 December 1598 a combined Korean and Ming fleet intercepted Japanese ships trying to relieve Konishi Yukinaga; Yi Sun-sin was killed in the battle. The last Japanese troops left Korea before the end of the year.

Key people

• Toyotomi Hideyoshi (1537–1598): ruler of Japan who ordered both invasions but never went to Korea himself.
• Yi Sun-sin (1545–1598): Korean admiral whose naval victories cut Japanese supply lines.
• King Seonjo (reigned 1567–1608): Joseon king who fled to Uiju on the Chinese border and appealed to the Ming.
• Yu Seong-ryong (1542–1607): chief minister who supported Yi Sun-sin and later wrote the Jingbirok, a key account of the war.
• Konishi Yukinaga and Katō Kiyomasa: leading Japanese commanders and bitter rivals.
• Li Rusong (died 1598): Ming general who retook Pyongyang in 1593.

Consequences

Korea suffered enormous losses. Cities, palaces and temples were burned, including Gyeongbokgung Palace in Hanseong, and famine and epidemics followed the armies. Estimates of Korean deaths vary widely, from several hundred thousand to more than one million. Records suggest that the area of registered farmland fell sharply, reducing royal revenues for decades.

Tens of thousands of Koreans were taken to Japan as captives. Among them were potters who founded important Japanese ceramic traditions, including the porcelain industry at Arita. Japanese soldiers also took books and movable metal type, and the Mimizuka (“Ear Mound”) in Kyoto holds noses and ears cut from Korean and Chinese dead as trophies.

Diplomatic relations between Korea and Japan were restored only after Hideyoshi’s family had lost power. Tokugawa Ieyasu, keen to reopen trade, returned some captives, and in 1607 a Korean embassy travelled to Edo. The Treaty of Giyu of 1609 with the Sō family of Tsushima reopened limited trade through a Japanese trading post at Busan, and later Korean embassies visited Japan at intervals until 1811.

For Ming China the war was one of the “Three Great Campaigns” of the Wanli Emperor. Its cost drained the treasury and weakened the Ming military in the north-east, where the Jurchen leader Nurhaci was building a new power that would later found the Qing dynasty. In Japan, the war divided Hideyoshi’s lords and helped prepare the conflict that ended at the Battle of Sekigahara in 1600.

Myths and facts

The war is sometimes presented as an attack on Korea alone. Hideyoshi’s declared goal, repeated in letters to Korea, the Ryukyu Kingdom and even the Spanish in Manila, was the conquest of China; Korea was to be the road. That plan collapsed within the first year, when it became clear that Japan could not supply armies deep in the peninsula.

Yi Sun-sin’s turtle ships are often called the world’s first ironclads. Contemporary sources describe a roofed deck covered with spikes, but whether it was plated with iron is not clearly documented, and historians remain divided. Only a few turtle ships were built; most of Yi’s fleet consisted of panokseon.

It is also sometimes claimed that Korea was saved by the navy alone. In fact the Ming army, Korean regular forces and the righteous armies were all essential to stopping the Japanese advance on land.

Timeline

• 1592, 23 May: Japanese troops land at Busan.
• 1592, 12 June: Hanseong (Seoul) falls to Konishi Yukinaga.
• 1592, 14 August: Yi Sun-sin wins the Battle of Hansando.
• 1593, 8 February: Ming and Korean forces recapture Pyongyang.
• 1593, 14 March: Gwon Yul defends Haengju fortress.
• 1596: Peace talks collapse after the Ming embassy to Hideyoshi.
• 1597, 28 August: The Korean fleet is destroyed at Chilcheollyang.
• 1597, 26 October: Battle of Myeongnyang.
• 1598, 18 September: Hideyoshi dies; withdrawal is ordered.
• 1598, 16 December: Battle of Noryang; Yi Sun-sin is killed.

Why it matters

The Imjin War was a true regional war involving the three main states of East Asia, fought with mass armies, firearms and fleets. It devastated Korea, shaped Korean national memory around figures such as Yi Sun-sin, contributed to the decline of the Ming and the rise of the Manchus, and left a legacy of mistrust between Korea and Japan that lasted for centuries.