Japanese Invasions of Korea

The army that Toyotomi Hideyoshi dispatched to Korea in May of 1592 was the product of the preceding decades of warfare in Japan, in which arquebuses and infantry warfare had become increasingly important. This shift from earlier practice continued during the campaigns against first the Koreans, and then the Ming Chinese forces that came to their aid. Over the course of the invasions the Japanese increased the number of arquebuses fielded by the army, together with the number of cannon employed by the navy. It availed them very little, because Hideyoshi’s basic strategy was so deeply flawed. His grand plans to conquer China were entirely unrealistic, let alone his even more far-fetched idea of going on to conquer India. On the operational level, Hideyoshi on the one hand failed to secure control of the sea between Japan and Korea and, on the other, failed to plan for a lengthy stay in Korea (beyond promising the lands that would be conquered to his troops). Hideyoshi seems to have believed that the Japanese army would be so tactically superior that battlefield victories would overcome any other problems. Not only did the Japanese army not win every battle, its initial successes exacerbated, rather than ameliorated, Hideyoshi’s fundamental operational and strategic mistakes.

In 1586, Hideyoshi sent envoys to the Korea court to ask them to help him in his plan to conquer Ming China. The Koreans rejected this idea, and Japanese envoys continued to attempt to persuade the Korean king for the next few years, without success. The king and his court were concerned about a Japanese invasion, but they were uncertain whether Hideyoshi was really intending to invade or just posturing. On several occasions, Japanese envoys presented the Koreans with Portuguese-style arquebuses, perhaps to demonstrate the sort of high-tech weapons they possessed. A Korean embassy to Japan, in turn, presented the Japanese with Portuguese cannons. Neither side was entirely clear on the other’s intentions. The Korean court was divided by factions with vastly different assessments of the likelihood of invasion, and both main factions corresponded with the Japanese. The Koreans also understood that Hideyoshi’s plan to conquer China was impossible. Hideyoshi, for his part, could not accept the Koreans’ unwillingness to assist him, or to recognize his great- ness. He was confident that the Chinese would simply flee at the sight of his army. By 1591, Hideyoshi resolved to punish the Koreans on his way to conquering the Ming.

Hideyoshi claimed he would raise an army of a million men, which would include some 300,000 arquebuses. The actual invasion force was about 160,000 men, with another 140,000-man reserve mobilized for a possible second wave. A large part of this army was composed of veteran warriors and experienced generals, but there was also a significant component of non-samurai, who were in many cases the men armed with arquebuses. This distinction is reflected in some of the letters sent home by Japanese leaders, demanding that more arquebuses be sent and that even samurai should be so armed. The influence of the West is also apparent in that Konishi Yukinaga, one of the three overall commanders, was a Christian convert.

When the Japanese invasion began in 1592, the Koreans were woefully unprepared for it. The army was poorly trained, led, and equipped, with only the navy armed with some cannon. It proved impossible to oppose arquebuses with bows, because of the guns’ greater range. Despite a few brave stands, the Korean forces were quickly defeated and driven off the field and out of the cities. They fared somewhat better at sea, inflicting a good number of casualties on the Japanese with their cannon, but with the navy poorly led, the Japanese rapidly defeated it. Indeed, much of the initial failure of the Korean navy was self-inflicted with the commanders of both of the Kyongsang fleets ordering their own ships scuttled. Some Korean generals believed that Japanese arquebuses were too inaccurate and slow to be a threat, and paid a terrible price for that evaluation. A favorite Japanese tactic familiar to us from the previous chapter was to establish dug-in lines of arquebus men and induce the Koreans to charge them.

Korean resistance soon collapsed, and the major question for the Japanese commanders was whether to consolidate their initial gains in preparation for a more systematic advance and a possible defense against Ming troops if they intervened, or to try and seize the entire kingdom as quickly as possible. They chose the latter course, though Hideyoshi soon dispatched more troops to support them and admonished them to consolidate their positions. Korean guerrilla forces were already forcing the Japanese to travel in large groups, however, and the occupation was not proving as easy as the quick battlefield victories. The Japanese were also helped by the Ming army’s preoccupation with a revolt in Ningxia, which prevented the best Chinese generals and troops from immediately going to aid Korea. By the middle of the year, the Korean king had fled all the way to his northern border with China.

The tide began to turn with a Korean naval victory on June 16, when a fleet of eighty-five ships cobbled together under the command of Yi Sun-sin destroyed twenty-six Japanese ships at Okpo off the southeast coast. Admiral Yi began a string of naval victories using the superior seamanship and cannons originally developed to deal with the wokou. A new Korean warship, the turtle boat, saw its first use in these battles, and proved devastating. The turtle boat was an oared ship about 34 meters long, with thick wooden planks and metal spikes covering the deck, armed with one or two large guns, and forty or more smaller guns. Japanese ships depended upon their arquebus fire and boarding tactics, leaving them almost helpless before an enemy who stayed at cannon range. When the Koreans did close with the Japanese, they made extensive use of bombs and other fire weapons. In short order, Admiral Yi crushed the Japanese navy, annihilating fleet after fleet with his superior tactics and weaponry.

Korean guerrilla activity was taking its toll on the Japanese even as Ming troops were beginning to trickle across the border. Just as Hideyoshi underestimated the Chinese, the Chinese underestimated the Japanese. Neither Japanese nor Chinese thought much of the Koreans, who were caught in the middle. Hideyoshi thought his army would be able to supply itself by light taxation on the Koreans at a level that would not instigate rebellion, but this generally failed. Japanese reprisals against Korean resistance were brutal, hardening Korean attitudes. In all of this, firearms were continually emphasized in the assistance the Ming court provided the Koreans, the warnings the Koreans gave the Chinese about the number of arquebuses possessed by the Japanese, and the tens of thou- sands of guns the Chinese commanders expected would be required to repulse the Japanese.

The Battle of Pyongyang on February 8, 1593 saw a head-to-head clash between the Ming-Korean army and the Japanese defenders of the city. The city was captured in a brutal assault backed by cannons, fire-arrows, and smoke bombs. Fierce hand-to-hand street fighting dislodged the Japanese, who lost 6,000-7,000 men in the city, another 6,000 who drowned while fleeing, and several hundred more to planned ambushes. Ming dead numbered about 800. The Japanese army had never before faced the sort of firepower brought to bear on them in Pyongyang. This was in many ways the decisive battle of the war, and all subsequent campaigns. The Japanese saw that they could not face Ming cannon, and that as long as the Ming supported the Koreans, they could not conquer Korea. After the Battle of Pyongyang they avoided direct clashes with Ming forces armed with cannon, preferring ambushes and hit-and- run tactics. The Japanese were also required to defend a number of fortified positions.

This was not to say that the war was over; Japanese troops continued to acquit themselves well, fighting an essentially defensive war. Northern Chinese troops not only found Korea unsuitable for cavalry tactics, they found their armaments left them at a severe disadvantage in fighting the Japanese. Horses, bows, and short swords could not contend with muskets and Japanese long swords. Southern Chinese troops, in contrast, were extremely effective, fighting on foot and using polearms to counter Japanese swords. The Japanese abandoned Seoul on May 18, 1593, leaving a brutalized population and, surprisingly, significant amounts of supplies. Shortly after the Japanese captured the city of Chinju on July 27, after fierce fighting, and slaughtered perhaps 60,000 inhabitants, peace talks began between the Ming and Japanese. The majority of Ming troops withdrew from Korea as a gesture of good will, leaving behind a small force to train the Korean army, particularly in firearms, and the Japanese fell back to positions on the southeast coast.

The years of farcical diplomacy that followed need not concern us here, but it seems clear from most accounts that not only did the negotiators repeatedly deceive their own masters, but Hideyoshi also did not really understand the military situation in Korea. The Japanese leader seems not to have grasped that his armies had been, in fact, badly beaten on several occasions, and that his grand design was entirely in ruins. Hideyoshi ordered a second invasion of Korea, this time to punish the Koreans, who he felt had slighted him, and to vent his fury at the Ming’s unwillingness to acknowledge his greatness. It was a pointless and tragic military adventure, even more filled with Japanese atrocities against the Koreans.

When the second invasion began in 1597, the Japanese had learned enough about the strength of the likely Ming response to proceed cautiously. They had also increased the number of ships transporting troops to Korea, though without really adapting to the Korean and Chinese navies’ superior naval technology. Neither the Koreans nor the Chinese, however, had increased naval strength in the interim in order to patrol the crossing points in strength. Indeed, a strong Korean or Chinese navy could have stopped the second invasion before it even really started. Japanese forces were entirely dependent upon food transported from Japan this time, because they had so badly destroyed Korea in the first invasion. Some of the Korean naval unpreparedness was likely due to Yi Sun-sin’s dismissal, after he fell foul of factional politics.

The Ming response was quicker the second time around, with somewhat more stress on shipbuilding, southern Chinese fighting techniques, and firearms. Even before the Chinese fully mobilized, the Japanese offensive collapsed short of reaching Seoul. This was due in part to a defeat at the Battle of Chiksan on October 16, 1597, when a Chinese ambush set up with many cannon crushed the advance guard of the Japanese forces advancing on Seoul, and in part to the arrival of the Chinese and Korean navy, with Yi Sun-sin back in command. On November 2, 1597, at the Battle of Myongyang, or the Miracle at Myongyang as some Koreans would have it, Admiral Yi annihilated a fleet of 133 Japanese ships. Once again, Korean ships armed with cannon, bombs, and smaller caliber firearms, and properly led, decisively defeated Japanese ships dependent upon arquebuses and boarding tactics. With the arrival of the Chinese navy in December, the supply lines to Japan were extremely tenuous.

Ming troops and material poured into Korea to push the Japanese out. By late December 1597, about 40,000 Ming troops, along with 1,000 cannon, 118,000 fire-arrows, almost 93,000 pounds of gunpowder, and more than 2 million pounds of bullets of all sizes were poised to attack Japanese positions. The initial push did not go well, and the war continued into the following year. By then it was clear even to Hideyoshi that the Japanese position was untenable. Even before he died in August, the Japanese began to withdraw. On December 14, at the Battle of Noryang Straits, a Chinese-Korean fleet destroyed more than two hundred Japanese ships with cannon fire. Admiral Yi was killed in this battle, but it was made clear at the end of it all, that Chinese and Korean naval tactics developed to fight the wokou were superior to Japanese boarding tactics.

The clash between differently armed gunpowder armies in Korea makes it clear how critical cannon, handguns, and bombs were in East Asian warfare in the late sixteenth century. Guns became more important over the course of the conflict, though each side tended to emphasize its manner of gun use, rather than adopt the methods of its opponents. This was not necessarily the paralyzing effect of a given group’s military culture; all sides could point to victories won using their particular methods. Neither side felt compelled to revise its technology, only its tactics. Here again, the results of the battlefield reinforced preconceived notions of warfare. People learned the lessons they were inclined to learn, and even those were strongly affected by their political implications.

FURTHER READING Albert Chan, The Glory and Fall of the Ming Dynasty, Norman, OK: University of Oklahoma Press, 1982. Jonathan Clements, Pirate King: Coxinga and the Fall of the Ming Dynasty, Stroud: Sutton, 2004. Edward L. Dreyer, Early Ming China, Stanford: Stanford University Press, 1982. Zheng He: China and the Oceans in the Early Ming, 1405-1433, New York: Longman, 2006. Peter Lorge, War, Politics and Society in Early Modern China, 900-1795, London and New York: Routledge, 2005. Joseph Needham, Science and Civilization in China, Vol. V, part 7: Military Technology: The Gunpowder Epic, Cambridge: Cambridge University Press, 1986. Henry Serruys, The Mongols and Ming China: Customs and History, London: Variorum Reprints, 1987. Kwan-wai So, Japanese Piracy in Ming China during the 16th Century, East Lansing: Michigan State University Press, 1975. Kenneth Swope, “The Three Great Campaigns of the Wanli Emperor, 1592-1600: Court, Military and Society in Late Sixteenth-Century China,” Ph. D. dissertation, University of Michigan, 2001. Arthur Waldron, The Great Wall of China: From History to Myth, Cambridge: Cambridge University Press, 1990. Kozo Yamamura, (ed.), The Cambridge History of Japan, Vol. III: Medieval Japan, Cambridge: Cambridge University Press, 1990.

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