Which 1600 battle established Tokugawa Ieyasu as Japan’s dominant military leader?

The Battle of Sekigahara in 1600 established Tokugawa Ieyasu as Japan’s dominant military leader.

The battle followed the death of Toyotomi Hideyoshi in 1598. Japan’s leading warlords divided into rival coalitions, with Ieyasu commanding the Eastern Army and Ishida Mitsunari associated with the Western Army. Their forces met at Sekigahara in Mino Province on 21 October 1600.

The battle’s outcome was influenced by shifting loyalties, including the late intervention of Kobayakawa Hideaki on Ieyasu’s side. The Eastern Army won decisively, and Ieyasu subsequently consolidated control over the country.

Ieyasu became shogun in 1603 and founded the Tokugawa shogunate. Sekigahara did not immediately eliminate every rival, however; the Toyotomi family remained powerful until the Siege of Osaka in 1614–1615.