What was the Battle of Mikatagahara?
Mikatagahara was the worst defeat of Tokugawa Ieyasu's life. Takeda Shingen, marching west with a large veteran army, drew Ieyasu out of Hamamatsu Castle onto open ground and destroyed his force in a winter afternoon.
Ieyasu survived, barely, and the campaign that would have carried Shingen into the heart of Oda Nobunaga's territory ended a few months later when Shingen fell ill and died.
Why did it happen?
By 1572 Shingen had joined the coalition against Nobunaga assembled around the exiled shogun Ashikaga Yoshiaki. His march west into Totomi and Mikawa was aimed at the Oda–Tokugawa alliance as a whole.
Ieyasu had perhaps 8,000 men and a relief contingent of around 3,000 from Nobunaga, who was fully occupied elsewhere. Shingen had roughly 25,000 to 30,000 by the usual figures. Ieyasu was advised to stay behind his walls.
When the Takeda army marched past Hamamatsu Castle without attacking it — heading for the road west — Ieyasu came out. Accounts differ on whether this was a calculated attempt to strike a marching column, an unwillingness to let an enemy cross his land unopposed, or a deliberate provocation by Shingen. All three explanations appear in the sources.
Forces and sides
Roughly 11,000 Tokugawa and Oda against roughly 25,000–30,000 Takeda, by the conventional figures. The disparity is not seriously disputed even if the exact numbers are.
What happened?
The Takeda were waiting in formation when the Tokugawa arrived on the plateau in late afternoon, in snow. Shingen had halted his march and turned to receive the attack rather than being caught strung out on the road.
The Tokugawa line broke within about two hours. Several senior Tokugawa retainers were killed covering the withdrawal, including men who deliberately impersonated Ieyasu to draw pursuit.
Ieyasu reached Hamamatsu Castle with a handful of riders. The best-attested part of the aftermath is that he ordered the gates left open and braziers lit; the Takeda advance guard, arriving in the dark, suspected a trap and did not press an assault.
Turning point
There was no turning point in the usual sense. The Tokugawa were outnumbered nearly three to one, on ground the Takeda had chosen, against the most experienced army in Japan. The interesting decisions all came before contact.
Outcome
The Tokugawa lost heavily — the usual figure is around 2,000 dead, against a few hundred Takeda — and Ieyasu's position in Totomi was badly shaken.
It did not last. Shingen fell ill during the following campaign season and died in the spring of 1573. The Takeda withdrew, and the threat evaporated. Two years later Ieyasu was on the winning side at the Battle of Nagashino when the Takeda army was broken.
Why it mattered
Mikatagahara is the defeat that Japanese tradition treats as Ieyasu's education. The story that he had a portrait painted of himself immediately afterwards, haggard and grimacing, to keep as a reminder of his own arrogance is famous — but the identification of the surviving painting with this battle is a later attribution that many art historians now reject.
What is solid is the pattern in his later career: at Battle of Komaki and Nagakute and again in the long approach to Battle of Sekigahara, Ieyasu consistently refused to fight on his opponent's terms.
