Even though the invasion of Korea was an act of unprovoked aggression by Japan against its immediate neighbour, the campaign has to be seen in the context of the overall strategic situation that existed in East Asia during the last quarter of the 16th century. It was a position dominated by China and its great empire of the Ming dynasty, whose pre-eminence was threatened in 1592 by a small island neighbour that had been obsessed with its own internal wars for over a hundred years. On previous occasions the lawless state of Japan had affected China in the form of pirate raids, but it was the very fact of Japanese disunity that had led it to pose no major threat to the stability of the Ming. This situation was to change radically in 1591, when Japan became reunited under one sword.
The reunification of Japan was achieved by Toyotomi Hideyoshi (1532–98). After a long military campaign that had reached from one end of Japan to another, Hideyoshi had brought to a close the century of sporadic civil war that historians have dubbed the Sengoku Jidai (The Age of Warring States), a term used by analogy with the period of that name in ancient Chinese history. It may therefore appear somewhat surprising that within one year of having achieved peace at home, the undisputed ruler of Japan should immediately seek war overseas; particularly when one considers that the Korean invasion remains the only major act of aggression by Japan against a neighbouring country within one thousand years of its history.
Admiral Yi Sunsin, the greatest hero of the defeat of the samurai invasion of Korea, is shown here discussing his plans for the battle of Okp’o, Korea’s first victory over the invaders as shown on this modern painting in the Okp’o Memorial Museum on Kŏje Island, South Korea.
Konishi Yukinaga, who played a prominent role throughout the campaign, leads a Japanese attack on Ming soldiers. From Ehon Taikōki, an illustrated life of Hideyoshi.
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. There is considerable evidence that he had been planning such a move for several years as the logical extension of his unstoppable triumphs at home. When Hideyoshi received Father Gaspar Coelho, the vice-principal of the Jesuit mission in Japan, in 1585, he disclosed to him his plans for overseas expansion and asked for two Portuguese ships to be made available, a request that was politely refused. Two years later, while setting off on the Kyūshū campaign, Hideyoshi told his companions of his intention to ‘slash his way’ into Korea and China. In fact his personal ambitions went further than Korea and China, and included the conquest of Taiwan, the Philippines and even India.
Hideyoshi’s expectation that an international act of aggression would be an unqualified success was fully in keeping with his experience of domestic Japanese warfare over the past two decades. As his power grew he would request rival daimyō (warlords) to pay homage to him and accept vassal status. If they refused they were attacked by Hideyoshi’s increasingly professional army. Hideyoshi was a generous victor, so that mass acts of suicide or battles to the death were rare events during his campaigns, and upon their submission the defeated daimyō were usually acknowledged in their existing possessions on agreeing to accept the status that they had once so unwisely declined. To treat Korea and even China in this way could well have seemed a natural progression for a successful general who had demonstrated, among his other accomplishments, the ability to move large numbers of soldiers over large distances, including across the sea. The Japanese army was well equipped and battle hardened, so to take on Korea and even Ming China with its vast resources theoretically available to oppose him, was not such a big gamble.
The horrors inflicted by the Japanese during the invasion of Korea brought back memories of the dark days of the wakō raids, as shown on this modern painting in the Okp’o Memorial Museum on Kŏje Island, South Korea.
From a wider political perspective Hideyoshi’s desire to make Korea and China into his vassal states may have been presumptive, but it was fully in the context of the way that international relations had long been handled from the Chinese side. To make China a vassal state of a neighbouring country would simply reverse the position that had existed for centuries, whereby China regarded itself as the centre of the world with its neighbours as its children. To the Ming emperors this dependent relationship was the basis of international trade and harmony. China was a universal and benevolent empire whose sovereignty had to be acknowledged by its less fortunate barbarian neighbours before the benefits of commerce could be bestowed. These supplicant barbarians must first pay homage to the Chinese emperor, who would then graciously bestow upon them titles and privileges such as being acknowledged by China as rulers of their own countries. In deep gratitude they would then bring tribute to his feet, and gifts would be showered upon them in return.
This exchange of tribute for gifts contained the essence of trade, and fruitful commercial transactions flowed from it, so most trading missions to China played along with the bizarre pantomime. Japan had always tended to be an exception to the rule, although, according to the first Ming emperor, the Japanese had entered into such a tributary relationship as early as the Han dynasty (202 BC to AD 220). In more recent memory the shogun Ashikaga Yoshimitsu (1358–1408) had indeed formally accepted vassal status and tribute trade had flourished, but with the collapse of the shogun’s authority during the Age of Warring States any kowtowing by Japan to China in this way had long ceased. Sino-Japanese relations were now characterized by an aggressive attitude towards international trading rights that was manifested through the depredations of the wakō (Japanese pirates). In spite of their name many wakō, and some of their most notorious leaders, were actually Chinese, who organized devastating raids against China and Korea from the 1540s onwards. In response the Ming had severed both trade and tribute with Japan, but as these independent-minded buccaneers lived outside the frame of Japanese legality anyway it was a slur that worried none of them. Some of their raids were so huge that they amounted to mini-invasions of China. Thousands of wakō would set up temporary headquarters in places like the Zhoushan archipelago off Ningbo, where they commandeered ships and horses and struck deeply into Chinese territory to rape and pillage with impunity.
Korea too had felt the brunt of the pirates. There was a wakō raid on Korea in 1544, and then in 1555 a much bigger operation was launched. In a chilling precedent for what was to come, Korean resistance all but collapsed. Left waiting for their commander to arrive from Seoul, the Korean troops gave in as soon as the Japanese advanced, and by the time the general arrived he had no army to lead – only runaway soldiers hiding in the forests and no one left in reserve.
The 1555 raid was almost a dress rehearsal for the officially sanctioned overseas expedition that was to hit Korea in 1592. It was launched to a background of ignorance on Hideyoshi’s part concerning the relationship between China and Korea and the likelihood that Korea would allow the Japanese army free passage to attack the Ming. Whereas Hideyoshi intended to turn the tribute system on its head by making himself ruler of China, successive kings of Korea had accepted their lowly tributary status willingly and loyally. As a result, when Korea was attacked by the nation whose outrageous behaviour had brought about the unthinkable insult of having its tribute status withdrawn, the Ming rushed to the defence of its faithful vassal. There may have been an element of self-interest in the Chinese response (a matter often exaggerated by an earlier generation of Japanese historians), but it was entirely selfless in its execution, and involved a huge commitment of resources and lives.
China also played a major role behind the scenes in the strategic build-up to the Japanese invasion. Because the depredations of the wakō were such a recent memory the Ming were acutely aware of Japan’s military strength and possible aggressive intentions, so as soon as there was evidence that Japan was planning an officially sanctioned invasion of the East Asian mainland they hurried to warn the Koreans. For purely logistical reasons any major invasion of China had to pass through Korea because the Japanese islands of Iki and Tsushima made the sea journey comparatively easy. When free passage for Japanese troops through Korea was refused a war against Korea as a preliminary stage of a war against China became inevitable.
Kuroda Nagamasa, commander of the Third Division, attacks the gate of the fortress of Hwangsŏksan during the second invasion of Korea in 1597.
According to the annals of the Ming dynasty it was also believed that the Japanese advance through Korea would coincide with wakō-like raids against Zhejiang and Fujian provinces in China. The likelihood of such a strategy explains why the first foreign monarch to hear of Hideyoshi’s plans was the king of Ryūkyū, the independent archipelago between Japan and Taiwan that is now part of Japan and is known by the name of Okinawa. The ‘southern route’ from Japan to China passes along the Ryūkyū islands, and Hideyoshi was concerned that the Ryūkyūans, who conducted active trade with China, might alert the Ming about his plans, so in 1589 he ordered Shō Nei, the new king of Ryūkyū, to suspend all trade missions forthwith. The king refused to do this, and in fact reported the matter to a group of Chinese envoys who were about to return home, urging them to inform their emperor.
Korean defences were characterized by low stone walls, as shown on this modern painting in the Memorial Museum at Ŭiryŏng. They were very vulnerable to the massed harquebus fire of the Japanese.
Another early warning of the invasion came to the ears of the Ming in 1591 from a Chinese trader who was captured by the Japanese. He managed to send a message back to Zhejiang saying that 100,000 Japanese troops were being massed to invade during the following year. This was very valuable intelligence, so the Wanli Emperor (r. 1573–1620) ordered that Chinese coastal defences should be strengthened. Representatives from Liaodong, the peninsula in northern China that would have been first to be attacked once Korea had fallen, sent word to the Korean king as soon as the news was conveyed to them. The Koreans certainly took the warnings seriously, and within two months a request for help from China was received at the Ming court. Its tone was optimistic with regard to the Chinese military capability, when it stated, that ‘When the celestial empire comes through the mountains with its great cannon, its mighty generals, heavenly firearms and fierce troops shaking the ground, even a million Japanese troops will not be enough to stop them.’
While the invasion fleet gathered, therefore, neither the Koreans nor the Chinese were in any doubt over what Hideyoshi was planning. It is also clear that the Koreans realized that they did not have the resources to prevent a landing or drive the Japanese back into the sea. Only the Ming could do that, and as Korea’s ‘elder brothers’ they were firmly committed to the task, so even before the first Japanese samurai had landed in Korea the strategic situation meant that three nations were prepared for war.