Japanese invasions of Korea (Imjin War)

The Imjin War is the name most often used in English for two Japanese invasions of the Korean kingdom of Joseon, in 1592 and 1597. “Imjin” is the name of the year 1592 in the traditional sixty-year cycle of East Asian calendars. In Korea the first invasion is called Imjin Waeran (“the Japanese disturbance of the Imjin year”) and the second Jeongyu Jaeran (“the second disturbance of the Jeongyu year”). In Japan the two campaigns are called Bunroku no eki and Keichō no eki, after the Japanese era names, and in China the war is remembered as the Wanli emperor’s Korea campaign.

Three countries fought. Japan, newly united under Toyotomi Hideyoshi, invaded. Joseon Korea defended its land. Ming China, Korea’s powerful neighbour and formal overlord, sent armies and fleets to help Korea, both because of their close relationship and because Hideyoshi openly said that his real goal was China.

The war lasted almost seven years, although the actual heavy fighting took place mainly in 1592–93 and 1597–98, with a long period of truce and negotiations in between. It was one of the largest wars anywhere in the world in the sixteenth century, and some historians call it the “Great East Asian War” because it drew in the whole region.

For more than a century Japan had been divided among warring lords, a period called the Sengoku (“Warring States”) era. Oda Nobunaga and then Toyotomi Hideyoshi reunified the country by force; Hideyoshi completed the job in 1590 by defeating the Hōjō family at Odawara. He now commanded hundreds of thousands of battle-hardened samurai and foot soldiers, many armed with arquebuses (early muskets) that Japan had adopted after contact with the Portuguese.

Hideyoshi announced that he would conquer Ming China and even beyond. He demanded that Korea let his armies pass through and join the attack. Joseon, which regarded Ming China as its senior partner in a long-standing tribute relationship, refused. Historians still debate Hideyoshi’s motives: personal ambition and a wish for glory, a need to reward and occupy his many warriors with new lands, the desire to control trade with China, or a mixture of these. Some scholars have also asked how seriously he understood the size of China.

In 1590 Joseon sent envoys to Japan to see what was happening. According to the traditional account, the chief envoy Hwang Yun-gil warned that Japan would attack, while his deputy Kim Seong-il argued that Hideyoshi was not a real threat. The two belonged to rival political factions, and the court was left divided. Historians note that Joseon did take some defensive measures, but its army had not fought a major war for a long time and was poorly prepared for a massive, well-armed invasion.

In the fourth lunar month of 1592 (late May in the Western calendar), the first Japanese division under Konishi Yukinaga landed near Busan. Fortresses at Busan and Dongnae fell within days; their commanders and many defenders and townspeople were killed. More divisions followed, and in total around 150,000–160,000 Japanese troops crossed to Korea in several columns.

The Korean general Sin Rip tried to stop the invaders at Chungju in June, but his cavalry was destroyed by Japanese musket fire. Only about three weeks after the landing, the Japanese entered Seoul. King Seonjo had already fled north, first to Pyongyang and then to Uiju on the Chinese border. Crown Prince Gwanghae led a separate “branch court” to keep the government working. Palaces in Seoul burned; the sources disagree about who set the fires.

The Japanese pushed on. Konishi took Pyongyang in the summer of 1592, and Katō Kiyomasa marched far into the northeast, where two Korean princes were handed over to him by local rebels. For a few months it looked as if Joseon might collapse completely.

At sea the story was different. Admiral Yi Sun-sin, commander of the Left Navy of Jeolla Province, attacked Japanese ships at Okpo in June 1592 and then won a series of victories. At Sacheon he used the geobukseon, or turtle ship, a covered warship with cannons. At the Battle of Hansan Island in August 1592 he lured a Japanese fleet into open water and surrounded it in a “crane wing” formation, destroying most of it. These victories made it very hard for Japan to send supplies and reinforcements by sea along the west coast of Korea.

On land, “righteous armies” (uibyeong) sprang up across the country. They were led by local scholars such as Gwak Jae-u and Jo Heon, and by Buddhist monks such as Hyujeong (Seosan Daesa) and Yujeong (Samyeong Daesa). These fighters knew the mountains and roads and attacked Japanese supply lines. At the first siege of Jinju in late 1592, the commander Kim Si-min held the fortress against a large Japanese force, though he was mortally wounded.

Ming China sent a first small force in 1592, which was defeated at Pyongyang. Early in 1593 a much larger army under Li Rusong, working with Korean troops, recaptured Pyongyang. The Ming then suffered a setback at Byeokjegwan north of Seoul, but in March 1593 the Korean general Gwon Yul defeated a large Japanese attack on the fortress of Haengju. Short of food and harassed on all sides, the Japanese left Seoul in May 1593 and withdrew to fortified camps on the south coast.

Even as talks began, fighting continued. In July 1593 the Japanese besieged Jinju a second time and captured it; Korean sources describe the slaughter of a very large number of soldiers and civilians. The story of Nongae, a gisaeng (female entertainer) who is said to have leapt into the Nam River while clasping a Japanese officer, became one of the best-known memories of this disaster, though details of the story come from later sources.

Peace negotiations were conducted mainly by the Ming envoy Shen Weijing and the Japanese commander Konishi Yukinaga, largely without the Korean court. Both negotiators appear to have misrepresented the positions of their own sides to reach an agreement. Hideyoshi’s demands included a Ming princess as a consort for the Japanese emperor, the southern provinces of Korea, trade rights and Korean hostages. The Ming court, in contrast, expected Hideyoshi to accept investiture as a vassal “King of Japan”.

In 1596 a Ming embassy invested Hideyoshi with that title in Japan. When it became clear that none of his demands would be met, he decided to renew the war. A popular story says that he tore up the Ming patent of appointment in anger, but a document identified as that patent survives in Japan, so historians treat the story with caution. The main point is clear: the negotiations had been built on misunderstandings, and Korea, whose land was at stake, had been largely shut out of them.

Japan sent about 140,000 troops again in 1597. This time its armies aimed first at the southern provinces, especially Jeolla, which had escaped the worst of the first invasion. Just before the attack, Yi Sun-sin had been arrested, tortured and demoted after refusing an order he considered reckless, a result partly of court politics and a Japanese deception. His replacement, Won Gyun, led the Korean fleet to disaster at Chilcheollyang in August 1597, where almost the whole navy was lost.

Reinstated with only about a dozen ships, Yi faced a much larger Japanese fleet in the narrow, fast-flowing Myeongnyang Strait in October 1597. Using the strong currents and the narrowness of the channel, his thirteen ships beat back well over a hundred Japanese warships, sinking or disabling about thirty of them. On land, a Ming–Korean force halted the Japanese advance at Jiksan, and the invaders fell back to their coastal forts.

The second invasion was especially brutal toward civilians. Japanese commanders were ordered to send back noses as proof of the enemy killed, and noses were cut from soldiers and civilians alike. The fall of Namwon in 1597 was followed by a massacre. Ming and Korean forces then besieged Japanese forts at Ulsan, Sacheon and Suncheon, with heavy losses on both sides.

Toyotomi Hideyoshi died in September 1598, and the council ruling in his name ordered a withdrawal. As the Japanese tried to leave, a combined Korean and Ming fleet under Yi Sun-sin and the Ming admiral Chen Lin intercepted Shimazu forces in the Battle of Noryang in December 1598. Yi was killed by a bullet during the battle; tradition says he told those around him not to announce his death until the fighting was over. With Noryang the war came to an end.

No one counted the dead. Estimates of Korean deaths, from fighting, massacres, famine and epidemic disease, range from the hundreds of thousands to more than a million; the higher numbers are frequently cited but are not based on reliable population records. Ming losses are often put in the tens of thousands, and Japanese losses, including many deaths from cold, disease and hunger, at around 100,000. All these figures should be treated as rough estimates.

The war destroyed farms and irrigation, and famine followed. According to one frequently cited calculation, the amount of registered farmland in Joseon fell from about 1.7 million gyeol before the war to about 540,000 after it; part of this drop reflects lost tax registers rather than land that had physically disappeared, but it shows the scale of the disruption. Palaces, temples and archives burned; of Joseon’s four archives of royal annals, only the copy kept at Jeonju survived.

Tens of thousands of Koreans were taken to Japan as captives. Estimates vary widely, from about 50,000 to 100,000 or more. Some were sold into the Portuguese slave trade in Asia. Others were artisans, especially potters, whom daimyō brought to Kyushu and western Japan; their skills helped found famous Japanese ceramic traditions such as Arita porcelain and Satsuma ware. Korean scholars and books were also carried off. After the war only a few thousand captives were repatriated through diplomatic missions.

In Kyoto stands the Mimizuka (“Ear Mound”), built in 1597 over the noses taken from Korean and Chinese dead, estimated at tens of thousands. It is a painful reminder of the war’s cruelty and, for Korean visitors, a site of mourning; in Japan it is much less widely known.

Korea. The war forced deep reforms. The Border Defence Council (Bibyeonsa) became the central organ of government, and a new standing force, the Hullyeon dogam (Military Training Command), was set up in 1593 to train musketeers and other specialised troops. To pay for the war the government sold offices and ranks and issued blank certificates of status, loosening the old social hierarchy. Joseon’s debt of gratitude to the Ming for “restoring the nation” (jaejo ji eun) became a central idea in its later foreign policy and culture.

Japan. Hideyoshi’s heir was a small child, and the great lords who had led the invasions were split into rival camps. Within two years, at the Battle of Sekigahara in 1600, Tokugawa Ieyasu, who had not sent troops to Korea himself, defeated his rivals, and in 1603 he founded the Tokugawa shogunate. The Tokugawa made peace with Korea: diplomatic missions resumed in 1607, and the Giyu Agreement of 1609 restored trade through the island of Tsushima. Korean ceramics, printing technology and Neo-Confucian learning captured in the war influenced Japanese culture; the captured scholar Kang Hang, for example, is associated with the early Japanese Neo-Confucian Fujiwara Seika.

China. The Korea campaign was one of the Wanli Emperor’s “Three Great Campaigns” of the 1590s and cost the Ming treasury vast sums. Many historians link this financial strain, together with the diversion of Ming attention and troops, to the later rise of the Jurchen leader Nurhaci in Manchuria, who went on to found the state that became the Qing dynasty. How much the war actually contributed to the fall of the Ming in 1644 is debated; other scholars stress internal problems such as factional politics, fiscal policy and climate-related disasters.

In Korea the war is remembered above all as a national ordeal and as a story of resistance. Yi Sun-sin became the supreme national hero; his statue has stood in Gwanghwamun Square in Seoul since 1968, and his shrine at Asan is a national site. The righteous armies are honoured as proof that ordinary people defended their country, and the works of Yu Seong-ryong and others are read as lessons about unpreparedness. In the Joseon period itself, memory also centred on loyalty to the Ming; the Daebodan altar, built in the palace in 1704, commemorated the Wanli Emperor.

In Japan, memory has changed over time. During the Edo period, popular books and plays about Hideyoshi presented the campaigns as heroic adventures, and figures such as Katō Kiyomasa became legendary. In the modern imperial era, from the late nineteenth century, the invasions were sometimes invoked as a precedent for Japanese expansion into Korea. After 1945 Japanese school textbooks increasingly described the war as an act of aggression, and many Japanese historians study it critically; nevertheless, sites like the Mimizuka remain relatively little known to the Japanese public.

In China, the war appears in the official Ming History and later writings mainly as a successful campaign in defence of a loyal tributary state, though Ming commanders were also criticised by contemporaries. Modern Chinese and Western historians such as Kenneth Swope have argued that popular Korean and Western accounts, which focus on Yi Sun-sin and the righteous armies, understate the Ming army’s role in the land war. Korean historians, in turn, emphasise that Korean forces, not only allies, bore most of the fighting and suffering. Presenting these perspectives side by side shows that each national story highlights some truths while leaving others in the shadows.

Korean sources are unusually rich. The Annals of King Seonjo (Seonjo sillok) record court debates, reports and decisions, though the Annals were compiled after the war and were later revised under a different political faction, producing a “revised” version whose judgements on individuals sometimes differ. Yi Sun-sin’s war diary, the Nanjung ilgi, and his reports to the throne give a commander’s daily view and are inscribed in UNESCO’s Memory of the World register. Yu Seong-ryong, who was chief state councillor during the war, wrote the Jingbirok (“Book of Corrections”), which focuses frankly on Joseon’s own mistakes; it was later printed and widely read in Japan.

Japanese sources include letters and orders of Hideyoshi and daimyō, clan records such as those of the Shimazu, Nabeshima and Tōdō, and personal diaries. One important text is the diary of the Buddhist priest Keinen, who accompanied a daimyō army in 1597 and recorded with horror the killing and enslavement of Korean civilians. Clan records tend to exaggerate their own achievements and the number of enemies killed, and some were compiled much later.

Chinese sources include Ming court records (the Veritable Records of the Ming), the official Ming History (compiled in the Qing period), memorials by commanders such as Song Yingchang, and private writings. They often reflect bitter rivalries among Ming officials and generals, which affects how battles like Byeokjegwan or the siege of Ulsan are described. Numbers of troops, ships and casualties in all three bodies of sources are often inflated or contradictory, and historians must compare them carefully.

Naming itself is a historiographical question. The Korean term “waeran” (“disturbance by the Wae”, an old and pejorative word for the Japanese) frames the war as barbarian aggression; the Japanese terms “Bunroku–Keichō no eki” are neutral era names, while older Japanese texts spoke of a “conquest of Korea” (Chōsen seibatsu). English-language scholars have used “Imjin War”, “Japanese invasions of Korea” and, following JaHyun Kim Haboush and others, the “Great East Asian War” to stress its international scope.

A major debate concerns the relative importance of the Korean navy, Korean land forces, righteous armies and Ming troops in defeating Japan. Twentieth-century Korean historiography, shaped by colonial rule and national liberation, highlighted Yi Sun-sin and popular resistance. Kenneth Swope’s study of the Ming side (2009) argues that the Ming intervention was decisive on land and that the war shows the Ming state was still capable of major military action in the 1590s. Samuel Hawley’s narrative history (2005) draws on sources from all three countries. Haboush’s posthumously published work (2016) argues that the war, and especially the righteous armies and their writings, helped create a proto-national sense of Korean identity.

Other questions remain open: Hideyoshi’s real aims and his knowledge of Ming China; the role of firearms in the early Japanese victories and how quickly Korea and Ming adapted; the number and fate of captives; and how far the war weakened the Ming and prepared the way for the Qing. Research also increasingly looks beyond battles to environmental history, refugees, slavery, and the transfer of technology and knowledge between the three countries.