Sekigahara Campaign

The Sekigahara Campaign was a series of battles in Japan fought between the Eastern Army aligned with Tokugawa Ieyasu and the Western Army loyal to Ishida Mitsunari, culminating in the decisive Battle of Sekigahara. The conflict was sparked by a punitive expedition led by Ieyasu against the Uesugi clan in the northeastern Tōhoku region, providing Mitsunari with an opportunity to denounce Ieyasu in the name of the infant ruling taikōToyotomi Hideyori while the Tokugawa troops were in the field.

Much of the campaign consisted of a struggle to control key castles on the Tōkaidō and the Nakasendō, the main roads linking Edo and the capital of Kyoto. However, battles and sieges far from these key highways, both in the Tōhoku and in pockets of resistance around the capital, had wide-reaching effects on the manoeuvring and availability of troops for the decisive battle at Sekigahara. The campaign also spilled over briefly into the southern island of Kyūshū, but Ieyasu quickly ordered his forces to stand down following his victory for political reasons.

The campaign dramatically changed the political landscape of Japan, resulting in the ascendancy of the Tokugawa Shogunate over the Toyotomi clan and the shifting of political power between the various daimyō who participated in it.