Hideyoshi launched the invasion of Korea in 1592, with the aim of conquering Korea first and using it as a base for eventual conquest of China. As things turned out, although the superior Japanese army made great progress at first (starting from Busan, taking Pyongyang and most of the peninsula in 3 months), they could not advance any further and were pushed out of Korea eventually, in 1598. The way I see it, the Japanese had severe strategic shortcomings that made the stated goals (conquest of Korea and China) wildly unrealistic:

  • The Japanese navy could not match the Koreans, and thus were mostly limited to guarding the Tsushima supply route, greatly hampering the land advance
  • They met with strong guerrilla resistance, tying up scarce manpower in defensive operations
  • Korea was an important tributary state to China at the time, and the latter would not sit idly by

These shortcomings would have been obvious to any competent commander, and Hideyoshi was no slouch. So what reasons did Hideyoshi have to initiate the invasion in the first place? Were there political intrigues, domestic issues, was this a golden opportunity (relatively speaking), or just plain arrogance/stupidity on Hideyoshi's part?

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    They really wanted to sit on the Dragon Throne.
    – o0'.
    Commented Jan 9, 2015 at 17:25
  • 2
    I disagree with you that the Japanese navy could not have matched the Koreans. The Korean navy was not in a strong position at all. It was only the division led by Admiral Yi Sun-Sin that was better than the naval divisions that the Japanese reached were routed at the beginning of the war. The Japanese had no idea before starting the invasion that Admiral Yi's naval division existed. Admiral Yi himself was not highly regarded in the Korean court. He owed his rise to his friend who had become the prime minister of Korea.
    – Arani
    Commented Feb 15, 2015 at 13:25
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    About the guerrilla resistance, the Korean royal court was rather unpopular among the people, and the Japanese believed they would not support the king (which is, in a way, true). Only when the Korean king had almost given up fighting did the guerrilla resistance begin.
    – Arani
    Commented Feb 15, 2015 at 13:26

6 Answers 6


Hideyoshi's reasons were not singular. A number of factors motivated his invasion of Korea. Although speculative hypothesis regarding his mental state is popular, domestic pressure for expansion coupled with seemingly-promising opportunities sufficiently explains the decision.

TL;DR: Hideyoshi needed land and to keep his soldiers occupied. Korea was an easy target for both. He was also quite ambitious with grand dreams so conquering Korea had no downsides (or so it seemed).

I. He was Insane

A popular, though somewhat speculative, explanation is that Hideyoshi was simply delusional. As the theory goes, Hideyoshi's triumph after triumph in Japan led him to believe the world was his for the taking. In this view, he launched the invasion of Korea as the first (and logistically inevitable) campaign in a quest for world conquest. Military and resource realities were unimportant, since the megalomania of Hideyoshi's senior years was motivation enough for his foolish adventures.

A slightly toned down version would be to say that Hideyoshi had extremely grandiose ambitions. While not particularly persuasive as a reason in and of itself, ambitious aspirations certainly would provides an overall context for Hideyoshi's decisions.

Yet the Korean expedition did not come from nowhere, and the most important trigger to action was Hideyoshi's own grandiose dream of overseas military conquest ... in fact his personal ambitions went further than Korea and China, and included the conquest of Taiwan, the Philippines and even India.

- Turnbull, Stephen R. Samurai Invasion: Japan's Korean War, 1592-98. Cassell & Company, 2002.

These ambitions are well documented in many of his communications. For example, he spoke of his dreams to invade China when making requests via Portuguese missionaries for galleons to support the same. Of course, he rose from near-commoner status to the highest office in the Imperial Court. That sort of thing don't usually happen without more than a healthy dose of ambitions.

II. A Short, Victorious War

Now, conquering Korea was not that unrealistic. Hideyoshi had every reason to believe an invasion of Korea would go well. And in fact, it did. His well trained, battle-hardened veterans rapidly overran most of the peninsula, capturing even Pyongyang after just two short months. The Koreans were no match.

The reality was that Korea was extremely ill prepared for war. Its military was poorly trained, poorly equipped, and inexperienced. Divisive factional bickering occupied the national attention, while military defense was allowed to decay with neglect. What little preparations were made largely went to the northern borders, where the nomadic tribes of Manchuria were seen as the real enemies.

Korea was weakened politically by feuding bureaucratic factions in the capital, fiscally by the corruption of the bureaucratic apparatus and the failure to maintain tax revenues by the land and tribute taxes, and militarily by the neglect of defense, the under-registration of the adult male population for service, the exemption of slaves and yangban from military duty, the lack of training, and the failure to adopt firearms.

- Palais, James B. Confucian statecraft and Korean institutions: Yu Hyŏngwŏn and the late Chosŏn dynasty. University of Washington Press, 1996.

To a large extent, the Ming intervention dramatically halted a conquest that was nearly fait accompli. While we might think it obvious for China to step in, this was not necessarily true. In reality, the Ming Court was filled with incredulous voices when Korea's plea for help arrived. The Imperial Cabinet suspected that the rapid Korean collapse was a ruse, laid in cahoots with Japan to ambush Ming reinforcements. It took months of intense lobbying by the Korean government before a minor unit was dispatched to reconnoiter the peninsula.

[A]t the beginning of the Imjin Was China deeply suspected that very possibility. It took three months of intense Korean diplomacy to convince Ming China that Korea was not conniving with Japan against China.

- Beeson, Mark, and Richard Stubbs, eds. Routledge Handbook of Asian Regionalism. Routledge, 2012.

Moreover, the Japanese invasion occurred when the Ming Empire was heavily distracted. While Japanese troops landed in Korea, Ming forces were at Ningxia, preoccupied with a major border revolt. Bā Bài, a Mongolian commander, seized 47 forts in the region with support from foreign Mongolian tribes. The pacification of Ningxia was serious enough to take most of the year, and would go down in history as one of the Three Major Conquests of Wanli Emperor (intervention in Korea being another).

Again this is not a very persuasive reason in and of itself. The weakness of Korea does, however, mean that it was (seemingly) a great target of opportunity.

III. Political Capital

On a more practical level, Hideyoshi wanted to conquer Korea (and beyond) for the sake of his domestic political position. A successful invasion of the Korean peninsula would have provided him with important resources. Namely, land - and lots of it. Its value in the Japanese political landscape should not be overlooked. Land (or more precisely, the rice productivity of the land) was the measure of power, and the unit of rewards. It was the object of the samurai's desires.

[T]he invasion of Korea can be seen as the necessary next stage after the conquest of Kyushu in 1587 and the defeat of the Hojo in 1590. The invasion would provide new lands for his warriors and enable Hideyoshi to retain his control over them.

Van Derven, H. J., ed. Warfare in Chinese History. Vol. 47. Brill, 2000.

Hideyoshi was too generous a conqueror. Even while subjugating lord after lord in rapid succession, he generally allowed those who submitted to retain their core holdings. What lands he confiscated land were typically distributed to other samurai lords in return for their pledge of allegiance (as opposed to going to traditional vassals and family - both of which he had none/little). This strategy helped ensure the rapid capitulation of most of Japan, but it also meant a horde of powerful daimyos who had the means (of a large standing army) and the inevitable greed to expand their holdings.

Independent military initiatives by the daimyo to expand their domains at one another's expense would collide directly with Hideyoshi's aim of unification. Hideyoshi felt that he could achieve domestic peace and unity and bring an end to the daimyo's struggles among themselves, by redirecting their tremendous energy for independent action toward the conquest of the continent.

- Hall, John Whitney, ed. The Cambridge History of Japan. Vol. 4. Cambridge University Press, 1991.

Therefore, a nearly defenseless (or so it seemed) Korea provided a logical target for Hideyoshi. An invasion would serve his domestic political needs for land, a highly limited commodity, and maintain his rule. If they failed, they would have whittled their strength in a land war in Asia. In the event of a successful conquest, he could also transfer daimyos into ostensibly bigger territories in Korea, and out of Japan, as rewards. That Hideyoshi perhaps harboured grandiose dreams of being a continental conqueror was a big bonus, too.

Hideyoshi was inspired to invade the continent to keep the military momentum of his unification of Japan going. He saw continental warfare as a means to assert even firmer control over Japan's warrior class, and also to provide new lands to meet the still strong demands of the daimyos for territorial acquisition.

- Black, Jeremy, ed. War in the Early Modern World. Taylor & Francis, 1999.

IV. Unemployment Relief

This is closely linked to the previous section, but with the focus on the huge surplus military manpower Japan had upon unification. Late 15th century Japan was a highly militarised society that has spent more than a century in near-constant warfare before Hideyoshi's unification wars. The speed of his meteoric rise bears stressing. The last hold out, the Hōjō clan of Odawara, was conquered in 1590. It had only been eight years since the assassination of Oda Nobunaga.

Continuing a doctrine of forbidding private warfare, Hideyoshi issued sō buji rei to subjugated clans. This forbade the latter from engaging in warfare. Almost overnight, Hideyoshi's rapid pacification of Japan rendered massive, battle-hardened feudal armies out of work. The country had, for 130 years, oriented itself around fighting; there was no institution in place to absorb the hundreds of thousands who had heretofore made a living out of warfare.

Unemployed samurai, known as rōnin, were in particular a major security concern throughout Medieval Japan. The explosion in their numbers after the Sengoku period exacerbated the situation. Ronin revolts continued to rock the Tokugawa Shogunate well into the 1650, for example. Rather than sit tight and hope for the best, Hideyoshi found a massive public employment scheme in the form of an invasion of Korea.

V. Prestige

Some scholars have argued that Hideyoshi was primarily concerned with international fame. In this view, he didn't have to worry about guerrilla or garrisoning concerns; he only wanted to win. It is of course much easier to defeat a Chinese army than to occupy the whole of China. The latter might be too unrealistic to contemplate, but the former was well within the realm of capabilities.

[M]ost scholars point to status or economic - not military - consideration. For example, Swope notes that, `Hideyoshi craved recognition and homage from foreign rulers. This goal should not be trivialized', and Elizabeth Berry also concluded that, '[Hideyoshi] was clearly less interested in military dominion abroad than in fame'.

- Beeson, Mark, and Richard Stubbs, eds. Routledge Handbook of Asian Regionalism. Routledge, 2012.

This would be entirely in keeping with his past experiences. His modus operandi in the unification of Japan was to crush his enemy in decisive battles. Often this shock and awe convinced the independent-spirited daimyo to render homage, which point Hideoyhi generously confirm them in their possessions.

Of course, in reality this is not that applicable outside of Japan, but Hideyoshi was (take your pick) delusional/overconfident/naive/ignorant/hopeful. He did issues demands to his neighbours, to the effect of supplanting China as the centre of the tributary system.

  • Wanted to edit "gorilla" to "guerrilla" but system require six edits, so couldn't help you.
    – user293129
    Commented Feb 15, 2015 at 0:56

Hideyoshi's predecessor, Oda Nobunaga, ruled mainly through fear and intimidation. Hideyoshi had a more benign approach. When conquering Shikoku and Kyushsu he let the local daimyo keep their holding provided they swore him loyalty. Hence, there were no spoils of war to divide among his retainers to the same extent that Nobunaga was able to.

Megalomania is often used as a justification for Hideyoshi's plans for mainland Asia, but testing the loyalty of his new retainers from the western provinces, together with the need for war spoils to be divided among his old loyal retainers, at least provide for a more rational explanation for hist Korean invasion. There is no doubt that he thought highly of himself, after all he came from the lowliest of backgrounds, as witnessed by the letters he sent to rulers around southern Asia. Yet, he seems to have harbored plans for moving some of the western daimyo over to Korea and China, and then handing over their domains to his more trustworthy retainers.

The invasion went smoothly, too smoothly actually. The Korean army's leadership was determined by knowledge of Chinese classics, not martial prowess. The only exception was Admiral Yi, who thanks to local knowledge of turning tides in narrow straits was able to cause severe damage to Hideyoshi's fleet. It was first when the Ming emperor decided to intervene that the tide turned on land as well, so to speak. Just as with MacArthur, the Chinese were able to press the Japanese armies all the way back to Ulsan and Pusan.


I knew nothing about him before reading the Wikipedia article on him five minutes ago, so hopefully someone will come up with a more informed answer.

According to Wiki:

Hideyoshi's health beginning to falter, but still yearning for some accomplishment to solidify his legacy, he adopted Oda Nobunaga's dream of a Japanese conquest of China and launched the conquest of the Ming Dynasty by way of Korea (at the time Joseon).

It seems to me he wanted his place in History. He felt he wasn't going to live much longer and wanted to be remembered for a great accomplishment. That desire was probably stronger and more important, and the practicality or feasibility of the task was secondary. A form of gambling for immortality?

(He may have failed but here we are discussing him for that, so perhaps it did work to some extent :)


Japan has spent over a century in constant fighting when Hideyoshi unified the country. Typically Japanese conquerors take land from the defeated and reward their own followers. But with all of Japan conquered, there wasn't any new land to give away.

Conquering Korea solves both problems. Unfortunately for Hideyoshi, the invasion failed.


Actually, if you observe the older events between so called Korea and so called Japan, the Japanese themselves had great connections with two Korean states (there were three Korean states). Baekje and the other state Gaya had great connections with Japan state Yamato. The relationship was great, for example Baekje sent a letter to Yamato for help, two times Yamato sent troops, all were destroyed by Baekje and Yamato enemy Ming I think. Baekje state wanted troops to defend again the Chinese states, anyway the Japanese support was not useful, Korean states ended up collapsing to the so called Chinese. The collapsed Korean state then became Joseon. It was natural to attack southern Joseon because it was a former Silla, Silla was not Yamato's friend, Yamato's friend was Baekje and Gaya. Also, among European states, Portuguese were slave traders. Hideyoki wrote letters I believe to the Portuguese government, to give back kidnapped Japanese people (Portuguese were kidnapping and selling Japanese as slaves, Hideyosi didn't like that despite pro Japanese slavery existed I think, idk). Portuguese also liked going to Korea, kidnapping in Korea too I think. Its like a two problems solved with one action. And Hidesohi was a states leader, not a government. In other words, states attacked Korea with objectives, not a government.

  • It's very difficult to understand what this answer is trying to say. I would suggest some spell-checking (for example, are Hideyoki, Hideyosi and Hidesohi different people or the same person?) and addition of links for some of the terms and events mentioned.
    – Steve Bird
    Commented Feb 7, 2017 at 15:07

The really short answer is: because he thought he could.

The Japanese acquired what they felt were superior war making technologies from Europe, specifically the ability to mass produce a musket of Portuguese design and V-shape hulled ships.

That he believed was enough to make him the master of East Asia. Korea was simply going to be his launching pad into conquering Ming China.

And that really was all it took for him to justify his war.

Unfortunately for him, on land massed musket was not decisive enough. Though it did give him a number of early victories against korean ground forces. But once they started having problems at sea which impacted their supply line, the Korean forces, vastly reinforced the arrival of a Ming army, were able to turn the tide on land.

At sea the doctrine of raking the enemy deck with musket fire was effectively countered by the turtle ship design (with a roof on top). Making things even worse for him at sea was the fact that speed giving V-shape hull was not particularly well suited for littoral combat by the Korean coast line, where maneuverability trumped sustained speed. And the korean ships carried vastly more cannons.

Turned out cannons trumped muskets in naval warfare... who knew?

Hideyoshi clearly didn't. And when things didn't go as planned, he didn't back down and let the war drag on for 8 years. As a result, the Toyotomi clan was soon kaput.

Hence the saying: Oda Nobunaga pounded the rice. Hideyoshi baked the cake and Tokugawa Ieyasu ate it.

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