The castle rose in under six months. That was the first sign that something extraordinary — or catastrophic — was coming.

Nagoya Castle (名護屋城, Nagoya-jō), constructed in Hizen province (modern Karatsu, Saga Prefecture) from early 1591, was not a defensive fortification. It was a forward operating base. Perched on the Kyushu coast with the Korea Strait glittering beyond its walls, it was designed to receive, quarter, and launch the largest overseas army Japan had ever assembled. Daimyo (大名, daimyo) from across the country were summoned not just to send troops but to build their own subsidiary encampments around the main castle. At its peak, the Nagoya complex hosted a city-sized military population.

By mid-February 1592, the orders had been circulating for months. Toyotomi Hideyoshi (豊臣秀吉, Toyotomi Hideyoshi) — born the son of a peasant foot soldier, risen through sheer tactical genius and ruthless political instinct to become the undisputed ruler of Japan — had decided that a unified Japan was insufficient. He wanted Korea as a staging ground. He wanted to march through Korea and take Ming China. Some sources suggest he spoke of India beyond that. Most historians treat the India claim as rhetoric. The China claim was entirely serious.

Approximately 158,000 warriors, plus 9,200 naval personnel, assembled along the Hizen coast and on the island of Tsushima (対馬, Tsushima). The crossing to Busan launched on May 23, 1592. The initial advance was staggering in its speed: Seoul fell nineteen days after the first landing. Korean defenses collapsed against the Japanese use of firearms — arquebuses (鉄砲, teppō) that the Koreans had never faced in battle at this scale.

Hideyoshi sat in Nagoya Castle and watched reports arrive. He never crossed the water. In six years of war, the man who ordered the conquest of Korea never set foot on Korean soil.

The invasion's undoing came not on land but at sea. Admiral Yi Sun-sin (이순신) of the Joseon navy had never commanded a naval battle when the Japanese fleet appeared in Korean waters. The Korean navy was small and outmatched on paper. It won anyway. At the Battle of Hansan Island (閑山島の戦い, Hansan-jima no tatakai) in August 1592, Yi lured the Japanese fleet into open water and deployed the "crane wing" formation. Fifty-nine Japanese ships were sunk or captured. The defeat was so catastrophic that Hideyoshi personally ordered all Japanese naval operations halted — effectively abandoning his own armies' supply lines on the Korean peninsula.

What followed was six years of grinding stalemate. Japanese armies held territory but could not advance. Korean and Chinese Ming forces wore them down through irregular warfare and conventional counterattacks. The soldiers were ordered to cut off enemies' noses and ears — too many heads to transport across the Korea Strait as proof of kills. The resulting pile was enshrined in Kyoto as the Mimizuka (耳塚, Mimizuka), the Ear Mound, which still stands today, containing the severed noses of at least 38,000 Koreans and 30,000 Chinese soldiers.

A second invasion in 1597 fared no better. When Hideyoshi died on September 18, 1598, his Council of Five Elders (五大老, Go-Tairō) secretly suppressed the news while quietly arranging the withdrawal of all Japanese forces. The commander who had won every campaign in Japan had spent the last six years of his life presiding over a war he could not win.

The consequences rippled far beyond Korea. The campaigns exhausted the Toyotomi treasury and consumed the fighting strength of the daimyo most loyal to Hideyoshi. One man had been conspicuously conservative with his forces: Tokugawa Ieyasu (徳川家康, Tokugawa Ieyasu), who sent troops to Korea but never committed his best armies. When Hideyoshi's heir proved unable to hold the coalition together, Ieyasu was waiting. The Battle of Sekigahara (関ヶ原の戦い, Sekigahara no tatakai) came in 1600. The Tokugawa shogunate (徳川幕府, Tokugawa Bakufu) followed in 1603.

The invasion Hideyoshi ordered from Nagoya Castle did not merely fail. It cleared the road for the dynasty that replaced him.