Hideyoshi took Seoul in twenty days — then the war ate his army and his dynasty

In 1592, Toyotomi Hideyoshi dispatched approximately 250,000 men to Korea, intending it as a corridor for the conquest of Ming China. Japan had just emerged from decades of civil war, leaving an immense body of trained veterans with no war to fight. The invasion gave them one. Seoul fell within twenty days; the Korean king fled by night along the road to China.

The advance outran its supply line. Admiral Yi Sun-sin, commanding the Korean fleet in the south, used iron-plated 'tortoise boats' to destroy a Japanese reinforcement fleet carrying 60,000 troops. By 1596, on Hulbert's account, Japan had lost 180,000 men to Yi's interdiction. The Japanese army, cut off from resupply, entrenched on the southern coast and lived off the land while guerrilla bands bled it.

A second invasion landed in 1597 with 1,000 boats, but Korea was now armed, trained and familiar with Japanese methods. Allied Korean and Chinese forces defeated a Japanese column at Chiksan, ending any attempt on Seoul. In 1598, the Japanese tried to sail home; Yi Sun-sin destroyed almost the entire fleet in the war's final naval battle. He was mortally wounded in the engagement.

The war achieved nothing. China was never invaded. Korea was devastated but freed. The Toyotomi military was hollowed out. Two years after Hideyoshi's death in 1598, his loyalists were too weakened to hold power: Tokugawa Ieyasu defeated them at Sekigahara in 1600, and the Toyotomi line was extinguished at Osaka in 1615.