Tokugawa Ieyasu won the Battle of Sekigahara on October 21, 1600. The clash decided who would rule Japan after the death of Toyotomi Hideyoshi, the man who had nearly unified the country. It was the largest battle fought on Japanese soil.
The day began in fog. Two coalitions met in a mountain valley, and for hours the outcome hung in the balance, with neither side able to break the other. The turn came when several lords on the western side switched allegiance mid-battle and fell on their own allies. The line collapsed after that.
The western army was shattered. Its leader, Ishida Mitsunari, was captured and executed, and the victors rewarded the lords who had switched sides, a fact that shaped the politics of the new order. The battle itself was over by dusk. The consequences lasted centuries.
Ieyasu became shogun three years later. The Tokugawa family ruled from Edo for more than two hundred and fifty years, and the country entered a long peace that it had not known in centuries. The era of warring states ended at Sekigahara.
The battle fixed the shape of Japan. The samurai who fought there became the hereditary ruling class, and the peace they enforced closed the country to the world for generations. A single day in a foggy valley settled the next two and a half centuries.