In 1592, and again in 1597, Toyotomi Hideyoshi, aiming to invade China (唐入り) through Korea, mobilized an army of 160,000 peasants and samurai and deployed them to Korea. (See Hideyoshi's invasions of Korea, Chōsen-seibatsu (朝鮮征伐?). Taking advantage of arquebus mastery and extensive wartime experience from the Sengoku period, Japanese samurai armies made major gains in most of Korea. Kato Kiyomasa advanced to Orangkai territory (present-day Manchuria) bordering Korea to the northeast and crossed the border into Manchuria, but withdrew after retaliatory attacks from the Jurchens there, as it was clear he had outpaced the rest of the Japanese invasion force. A few of the more famous samurai generals of this war were Katō Kiyomasa, Konishi Yukinaga, and Shimazu Yoshihiro. Shimazu Yoshihiro led some 7,000 samurai and, despite being heavily outnumbered, defeated a host of allied Ming and Korean forces at the Battle of Sacheon in 1598, near the conclusion of the campaigns. Yoshihiro was feared as Oni-Shimazu ("Shimazu ogre") and his nickname spread across not only Korea but to Ming Dynasty China. In spite of the superiority of Japanese land forces, ultimately the two expeditions failed (though they did devastate the Korean landmass) from factors such as Korean naval superiority (which, led by Admiral Yi Sun-shin, harassed Japanese supply lines continuously throughout the wars, resulting in supply shortages on land), the commitment of sizeable Ming forces to Korea, Korean guerrilla actions, the underestimation of resistance by Japanese commanders (in the first campaign of 1592, Korean defenses on land were caught unprepared, under-trained, and under-armed; they were rapidly overrun, with only a limited number of successfully resistant engagements against the more-experienced and battle-hardened Japanese forces - in the second campaign of 1597, Korean and Ming forces proved to be a far more difficult challenge and, with the support of continued Korean naval superiority, limited Japanese gains to parts southeastern Korea), and wavering Japanese commitment to the campaigns as the wars dragged on. The final death blow to the Japanese campaigns in Korea came with Hideyoshi's death in late 1598 and the recall of all Japanese forces in Korea by the Council of Five Elders (established by Hideyoshi to oversee the transition from his regency to that of his son Hideyori).
When was the Battle of Sacheon?
1598