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Shawn Ford
Term Paper
Spring 1997

Note: The following article was written as the term paper for History 241W: Asian History from the 15th Century to Present, instructed by Loretta Pang at Kapiolani Community College. This paper originally appeared in the 1997 edition of Horizons, Kapiolani Community College's student journal of Asian and Pacific writing. Please pardon any errors or omissions. Refer to Works Cited for further details and additional information.

The Failure of the 16th Century Japanese Invasions of Korea

During the last decade of the sixteenth century, Japan, under the leadership of the general Toyotomi Hideyoshi, launched two unsuccessful military invasions against the Korean peninsula. The overall goal of these two invasions was to gain a foothold on the mainland and then use Korea as a stepping-stone to invade and conquer China. After nearly seven years of warfare and truce talks in Korea, Japan failed at its goal as a combined result of the brilliant naval command of Korean Admiral Yi Sun-sin, constant Korean guerrilla activity, Korean military assistance by Ming China, and lastly, the death of General Hideyoshi.

General Toyotomi Hideyoshi
Ancient map of Japan and Korea

Hideyoshi had spent most of the previous decade involved in almost constant campaigns to unify Japan. He finally achieved this unification in 1591 with the subjugation of Northern Honshu province1. With this task complete, he began to set his sights on other lands to conquer. While struggling for unification in 1585, he had already begun looking beyond his unification of Japan by making plans to invade China. In 1577, as an officer under General Oda Nobunaga, Hideyoshi had dreamt of the conquest of China for the glory of Japan2.

After gaining firm control over Japan, Hideyoshi sent envoys to Korea to re-establish relations with them. Relations had been strained due to many decades of uncontrolled Japanese pirate attacks against Korean port cities3. The envoys presented the request for normalization of relations to Korea's King Sonjo on the condition that he allow the Japanese army free passage through his country on its way to invade China. Korea was eager to re-establish ties with Japan, but not that eager. For many centuries, Korea had been a vassal state of China, and it was not prepared to ruin this relationship; therefore, the Japanese request was flatly refused.

However, King Sonjo was concerned about Hideyoshi's plans, so he in turn sent envoys to Japan in an attempt to discover Hideyoshi's true intentions. These envoys returned with contradictory reports. King Sonjo chose to listen to the envoy who advised that Japan would not attack Korea. Using this information, no military preparations were made for the defense of the Korean peninsula4.

Meanwhile, General Hideyoshi mobilized an army of 225,000 men for an invasion of Korea in the spring of 1592. At the core of this army was a large number of samurai, which consisted of elite horsemen and foot soldiers, battle hardened from years of civil war. The remainder was made up of conscripts, mostly commoners supplied from Japanese provinces that Hideyoshi had brought under his control during unification5. The army was well trained and armed with cannons, muskets, and long swords, and it was led by very capable commanders. These commanders were the daimyo, the local leaders of the provinces, who swore allegiance to Hideyoshi.

Hideyoshi also ordered the construction of an enormous staging area for the invasion at Nagoya on Kyushu, the point in Japan closest to Korea. The main invasion force massed there along with supplies for 480,000 soldiers. A large naval base was also built there, and the Japanese navy was assembled to transport the troops across the Tsushima Strait. This navy consisted of some 9,000 sailors aboard a massive fleet of small pirate vessels and large men-of-war6.

The order to launch the invasion was given in late April of 1592, and the first contingent of troops in 700 boats made landfall at Pusan on Korea's southern coast on May 23. Caught by surprise and outnumbered by soldiers with far superior weapons, the Korean defenders were quickly overwhelmed; the port city fell within a few hours7. Those Korean soldiers who did not die in the battle or who were not captured began to retreat inland in an attempt to reorganize.

The first three divisions of troops to land then began a three pronged attack northward across the Korean countryside and advanced rapidly towards the capital of Seoul. They met very little resistance until they reached Ch'ungju, neary two-thirds of the way to their destination. Here they encountered a reorganized Korean army under the command of war hero General Sin Ip. Although the defenders fought valiantly, General Ip and his soldiers were wiped out. Their rusty swords were no match against the Japanese soldiers' muskets. The city fell quickly, and the invasion force continued towards Seoul unchecked. Upon receiving this news, King Sonjo abandoned his capital and fled towards Uiju on the Yalu River in northwestern Korea8. The small contingent of troops he left behind for the defense of Seoul made a feeble stand along the Han River and was quickly overrun. Korea's capital of Seoul had fallen within three weeks of the start of the invasion9.

It was at this point that Korean Admiral Yi Sun-sin began to make his presence known to the Japanese. In 1591 he had been appointed Left Navy Commander of Cholla Province, charged with protecting Korea's southwest coast. This was considered a very important post, for through these waters flowed the bulk of Korea's grain reserves destined for the large cities of the north. These shipments had been susceptible to Japanese pirate attacks for decades. Given the history of these attacks, and coupled with the possibility of a large-scale Japanese invasion, which Admiral Yi saw as imminent, he began to build up Korea's navy. Admiral Yi directed the construction of a fleet of modern warships, including one ship that he designed himself, unlike any that the world had ever seen. He called his invention kobuk-son, the turtle ship10.

              The kobuk-son: Korea's turtle ship
Admiral Yi Sun-sin

This turtle ship, so named due to its shape, is considered to be the world's first ironclad battleship; however, there seems to be some disagreement about its exact design. The ship was lost long ago, and the only clues to its design come from written descriptions of it that are preserved in the Yi Sun-sin Shrine in Asan, Korea. Based on a reconstruction of the ship using these descriptions, its deck appears to have been covered with hexagonal iron plates that were spaced several inches apart from each other11. In the synopsis to Nanjung Ilgi, the writer says, "all important parts of the hull were covered with protective iron" (xxv). However, the reconstruction shows iron only on the deck of the ship. Another source states that the turtle ship was not an ironclad at all, but that it had a wooden deck "spiked with sharp pieces of metal" (Elisonas 278).

Although there are conflicting reports as to whether or not the turtle ship was clad in protective iron, there seems to be agreement on other specifications of the ship. Descriptions do suggest that the ship's deck was studded with long, sharp spikes. These spikes were used to discourage enemies from boarding the ship. Before going into battle, the deck was covered with straw mats to hide the spikes from the enemy. From descriptions of the turtle ship, it was a sturdy, flat bottom, wooden ship with a convex deck. It was ringed with up to 14 cannons, making it possible to fire in any direction. In addition, there were dozens of small gun ports around each deck that enabled the sailors inside to maneuver the ship and fire at will without being seen from outside. At the bow of the deck was mounted a figurehead in the shape of a dragon's head with four additional cannons inside of it. These cannons fired bombs of gunpowder and iron pieces while sending up smoke screens that made the ship difficult to pinpoint by Japanese gunners. The ship was equipped with 20 oars, making it possible to outrun any enemy vessel. It measured 110 feet from bow to stern, 28 feet across, and seven feet from the bottom of the boat to the bottom of the top deck. This was the largest of the turtle ships built, and it was commanded by Admiral Yi himself. Perhaps only four additional smaller ones were built for the war; unfortunately, none of them exist today12.

Side view of turtle ship construction Internal view of turtle ship

Special thanks to Jong-Soo Im, President of Model Turtle Ship Co., for turtle ship images, taken from the inside leaves of Admiral Yi Sun-sin's war diary, Nanjung Ilgi. For reconstructions from this original design, please refer to:

During the first year of the invasion, Admiral Yi engaged in ten successive naval victories that decimated the Japanese navy. At the battle of Okp'o, the Admiral's first victory, the Korean navy destroyed 31 out of 50 Japanese ships and only suffered one slight wound to one of its own sailors. Over the course of the next five battles, the Japanese lost 83 ships while the Koreans lost only 11 sailors. The next two battles, waged over a four-day period, are known together as the Battle of Hansan Island. It is regarded to be one of the three great Korean victories in the struggle against the Japanese13. In this battle, the Japanese navy lost 101 ships and more than 250 men, as opposed to 19 men lost on the Korean side. Admiral Yi won his ninth victory at the Battle of Pusan-p'o. His fleet of 92 ships, spearheaded by the turtle ship, encountered 470 Japanese vessels and sunk 100 of them while only losing only seven of his own sailors. A few months later, the Korean navy defeated the Japanese fleet at Ungp'o. With this tenth successive naval victory, Admiral Yi was appointed Supreme Naval Commander of the Three Southern Provinces14.

It should be pointed out that although the Japanese navy had a far greater number of ships and sailors than the Korean navy had, the Japanese navy was never a match for the superior Korean navy. The Japanese navy was made up mostly of trading vessels manned by sailors who had been pirates before the war. These men were not experienced with the forms of engagement that they witnessed in the Korean campaigns, and their ships were not equipped for such battles. Also, the Japanese naval commanders were unfamiliar with the waters along Korea's southern coastline, making it difficult for them to maneuver effectively. On the other hand, the Korean navy was composed of vessels built from knowledge gained while fighting against the Japanese pirates during the previous decades. Korean naval commanders and sailors also had received valuable training during this period, and their familiarity with the tides, currents, and obstacles of their home waters put them at a great advantage against the Japanese invaders15.

Under the leadership of Admiral Yi, the Korean navy was able to turn the tide of the invasion by cutting off the vital sea routes of the Japanese navy. Control of the Tsushima Strait and the numerous islets along Korea's southern coast had been an essential element of Hideyoshi's invasion strategy. Achieving this control would have given the Japanese navy access to the Yellow Sea, making it possible to re supply the Japanese troops in Seoul and P'yongyang by water; this would have also made it possible to set up fast communication links between Japan's northern and southern forces. With Korea in control of its own seas, Japan was forced to commit its navy to defending a narrow supply corridor between Kyushu and Pusan. From Pusan, the Japanese re supplied their northern forces via a precarious land route through central Korea. This method required much greater manpower than the sea route, and the Japanese supply lines were in constant threat of ambush by Korean guerrilla units16.

Within the first three months of the war, the Japanese invasion force had advanced up the Korean peninsula from Pusan in the south to the Yalu River in the north, capturing the major cities of Seoul and P'yongyang and routing the Koreans in every battle. The beleaguered Korean regular army, lacking leadership and morale, was scattered throughout the countryside into disorganized units. For a time, Korea was left virtually defenseless.

It was at this juncture that a guerrilla movement spontaneously began to develop all over Korea. Koreans from all walks of life joined guerrilla units that formed in their local districts and took up arms in the defense of their homeland. These guerrilla units were composed primarily of farmers and slaves and were typically led by either local gentry or respected Neo-Confucianists. Each unit generally was made up of a small number of men armed with swords and other light weapons; however, there were hundereds of these units throughout Korea.

Bands of guerrills repeatedly harassed Japanese communication and supply lines and attacked Japanese army columns using hit and run tactics. By the end of 1592 Korean guerrillas had succeeded in pushing the Japanese out of many towns and provinces throughout the country. At times more than one guerrilla unit joined with a reorganized Korean regular army unit to form a formidable host against the Jpanese invaders. In one instance a Korean force that had retaken a strategic fort at Haengju along the Han Rivernear Seoul fought back repeated attacks by a much larger Japanese force. The Korean victory at Haengju is also remembered to be one of the three great Korean victories against the Japanese. The Korean guerrilla movement that emerged, after the initial gains of the Japanese army, succeeded in stalling the momentum of the invasion and putting the Japanese on the defensive17.

Coupled with the successes of the Korean guerrilla movement was the entrance of the Chinese Ming army into the war. China finally came to the aid of Korea after repeated please by King Sonjo and after the Japanese army had already reached Korea's border with China. China was somewhat obligated to come to the assistance of Korea because Korea was a vassal state of China. Also, the threat of an invasion by Japan into China could not be tolerated. The first Chinese relief army of a mere 3000 troops arrived in Korea with the aim of retaking P'yongyang and was easily defeated by the Japanese occupiers. China then realized the seriousness of the situation that had developed in Korea, and they began to mobilize a much larger force to deal with the invading Japanese. In February of 1593, a Ming army of 50,000 soldiers attacked the Japanese defenses at P'yongyang and succeeded in pushing them all the way to Seoul before the Japanese counterattacked. Thus, a stalemate developed with the Chinese army in control of northern Korea and the Japanese in control of the central portion of the southern part of Korea from Seoul to Pusan.

At this point, informal talks were held between China and Japan, with the exclusion of Korea, to discuss the conditions for peace. After China threatened to send a 400,000 man army to Korea, Japan agreed to withdraw from Seoul and most of the Korean peninsula. By May of 1593, Japan retreated to a narrow defensive position along Korea's southern coast around Pusan, and formal peace talks were held. The peace talks between China and Japan over the fate of Korea were to last four years18.

China began the truce by sending emissaries to Japan to discuss peace between the two countries. General Hideyoshi was under the impression that Japan had won the war, so he gave his representatives at the peace talks a list of conditions for peace that were to be given to the Chinese delegation. These conditions included that the four southern Korean provinces were to be ceded to Japan, that a daughter of the Chinese emperor was to be wedded to the Japanese emperor, and that a Korean prince and several high ranking Korean officials were to be turned over to Japan as hostages to guarantee that the Korean government would no longer oppose Japan. Due to political intrigue on both the Chinese and Japanese sides, these conditions were not presented to the Ming emperor. Instead, a forged letter from Hideyoshi was given to the Ming emperor begging for peace and requesting that Japan be recognized as a vassal to China19.

After several years of delay, the Chinese emissaries returned to Japan in the fall of 1596 with the reply that the Ming emperor had bestowed on Hideyoshi the title of "King of Japan" and had recognized Japan to be a tributary state of China, with no mention of Japan's list of demands. This enraged Hideyoshi, as China's message to him was no more than one of Japan's subordination to China; therefore, Hideyoshi made plans for a second invasion of Korea20.

Japan launched its second invasion of Korea on August 27, 159721. Hideyoshi sent a force of 100,000 soldiers in 1000 ships to reinforce the 50,000 troops he had left in Pusan. This invasion began with a resounding victory by the Japanese navy, something it was unable to achieve even once during the first invasion. This Japanese naval victory could be due to the fact that Admiral Yi of the Korean navy had been imprisoned on false charges of misconduct and replaced with a rival commander prior to the second Japanese invasion22. However, even with this initial victory by its navy, during this invasion attempt the Japanese army was not able to advance very far into Korea. It met stiff resistance by a rearmed and reorganized Korean army backed by a huge Chinese army sent by the Ming emperor who had anticipated a second invasion of Korea by Japan. This time the Japanese did not reach Seoul but were stopped short of the city and were pushed steadily back towards Pusan23.

Meanwhile, the Japanese navy again suffered defeat at the hands of Admiral Yi who had been released from prison and reinstated as Supreme Naval Commander. At the Battle of Myongnyang in October of 1597, Admiral Yi's small contingent of twelve ships destroyed 133 Japanese vessels without any Korean losses. Admiral Yi achieved this victory after luring theJapanese fleet into a narrow channel and using the swift currents to his advantage24. This victory prevented the Japanese navy from entering the Yellow Sea and re supplying its army trying to advance towards Seoul25.

The Korean successes on land and at sea during the second Japanese invasion had the effect of containing the Japanese army to a narrow strip of land along Korea's south coast. Over the next year, the combined Chinese and Korean army constantly assaulted forts along the coast that were held by the Japanese. A determined Korean navy prevented the Japanese from re supplying these positions. The Japanese stubbornly tried to hold on to this territory so that their invasion attempts would not be a total loss.

The beginning of the end of the Hideyoshi invasions of Korea came about when General Hideyoshi died in Japan on September 18, 1598. The Japanese authorities who assumed control after he died realized that the war in Korea had to come to a swift end. After three more months of struggling to maintain control of their Korean forts, the Japanese gave orders for a retreat from Korea26.

The last battle of the war, the Noryang Sea Battle, was fought as one of the last contingents of troops was re embarking for Japan. A Japanese naval force 500 ships strong, sent to evacuate its remaining troops from Korea, was attacked by the Korean navy under Admiral Yi. More than 200 Japanese ships were sunk by the Korean navy that day. Unfortunately, with victory at hand, Admiral Yi was struck by a Japanese bullet and fell dead onto the deck of his flagship27. With this last battle of the Hideyoshi invasions of Korea, Korea lost one of its greatest war heroes.

Over the course of nearly seven years Japan tried to press its claims on the Asian mainland by attempting to conquer China through an invasion of Korea. In the end, General Hideyoshi's visions of a greaterJapan were dashed. The Japanese navy was never able to gain control of Korea's seas from Admiral Yi, therefore Japan's crucial supply lines to their mainland army were not secure. Japan's leaders underestimated the fighting spirit of the Korean people, having initially defeated the Korean army so easily. Hideyoshi also underestimated China's awesome war resources and its commitment to its little brother Korea. Even at the end, Japan wasunwilling to give up the invasion until General Hideyoshi had died. With Hideyoshi's death, and Japan's subsequent withdrawal from Korea, Japan failed at its attempt to conquer China with nothing gained while losing close to 100,000 soldiers in the process.


1 Jurgis Elisonas, “The inseperable trinity: Japan’s relations with China and Korea”, The Cambridge History of Japan. Ed. John W. Hall (Cambridge: Cambridge UP, 1991), 235-300.
2 Elisonas 267.
3 Andrew C. Nahm, Introduction to Korean History and Culture (Elizabeth, NJ: Hollym Corp., 1993).
4 Woo-keun Han, The History of Korea, Trans. Kyung-shik Lee, Ed. Grafton K. Mintz (Seoul: Eul-Yoo Pub., 1970).
5 Elisonas 272.
6 George Sansome, A Hostory of Japan 1334-1615 (Stanford: Stanford UP, 1961).
7 Sansome 354.
8 Ki-baik Lee, A New History of Korea, Trans. Edward W. Wagner (Seoul: Ilchokak Pub., 1984).
9 Elisonas 273.
10 Admiral Yi Sun-sin, Nanjung Ilgi: War Diary of Admiral Yi Sun-sin, Trans. Tae-hung Ha, Ed. Pow-key Sohn (Seoul: Yonsei UP, 1984).
11 Yi. See drawing and photo of the ship on opening pages of the book.
12 Sun-sin XXV.
13 Lee 212.
14 Yi XXVI to XXIX.
15 Sansome 354.
16 Elisonas 278.
17 Lee 212.
18 Elisonas 280.
19 Sansom 358.
20 Sansom 358.
21 Elisonas 286.
22 Yi XXIX.
23 Elisonas 287.
24 Yi XXIX.
25 Elisonas 287.
26 Elisonas 288-290.
27 Yi XXX.

Works Cited

Elisonas, Jurgis. "The inseperable trinity: Japan's relations with China and Korea." The Cambridge History of Japan. Vol. 4. Ed. John Whitney Hall. Cambridge: Cambridge UP, 1991. 235-300.

Han, Woo-keun. The History of Korea. Trans. Kyung-shik Lee. Ed. Grafton K. Mintz. Seoul: Eul-Yoo, 1970.

Lee, Ki-baik. A New History of Korea. Trans. Edward W. Wagner and Edward J. Schultz. Seoul: Ilchokak, 1984.

Nahm, Andrew C. Introduction to Korean History and Culture. Seoul: Hollym, 1993.

Sansome, George. A History of Japan. Stanford: Stanford UP, 1961.

Yi, Sun-sin. Nanjung Ilgi: War Diary of Admiral Yi Sun-sin. Trans. Tae-hung Ha. Ed. Pow-key Sohn. Seoul: Yonsei UP, 1977.

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contents (c) 2001 Shawn Ford/ Webb-Ed Press