1600
Battle of Sekigahara
The setting
Sekigahara, a mountain basin in Mino Province (modern Gifu Prefecture), central Japan
Narrow valley/basin at a strategic crossroads (the Nakasendo and Hokkoku roads), enclosed by wooded hills; the Western Army held surrounding heights such as Mount Matsuo and Mount Nangu.
Reveal the outcome
Recorded sideEastern Army (Tokugawa Ieyasu)
Recorded resultdecisive victory
Decisive Eastern (Tokugawa) victory, aided by the defection of Kobayakawa Hideaki
How the atlas explains it
The fight was decided less by maneuver than by politics. Tokugawa had secretly secured the defection of key Western commanders; at the crisis, Kobayakawa Hideaki turned his large force on Mount Matsuo against the Western Army (allegedly after Tokugawa fired on him to force his hand), and other contingents (e.g., Wakisaka and others) followed or simply refused to engage. The Western flank collapsed, morale broke, and the encircling position fell apart. Intelligence and pre-arranged betrayal, not numbers, were decisive.
What followed
The decisive battle of the Sengoku period; cleared the way for Tokugawa Ieyasu to become shogun in 1603 and establish the Tokugawa shogunate, beginning ~250 years of relative peace (Edo period).