In October 1572, after having concluded alliances with his rivals to the east (the Later Hōjō clan of Odawara and the Satomi clan of Awa), and after waiting for the snow to close off the northern mountain passes against his northern rival, Uesugi Kenshin, Takeda Shingen led an army of 30,000 men south from his capital of Kōfu into Tōtōmi Province, while Yamagata Masakage led a second force of 5,000 men into eastern Mikawa Province.

[3] Against the advice provided by Sakuma Nobumori and Takigawa Kazumasu, who had been sent by Nobunaga, and by his own generals, Matsudaira Koretada (Fukōzu) and Ishikawa Kazumasa, Ieyasu refused to allow the Takeda to pass through his territory unhindered, and drew up his forces on a high plain called Mikatagahara, at the time located just north of Hamamatsu.

[2][4] According to the Kōyō Gunkan, the contemporary Takeda military history, Shingen outnumbered Ieyasu three-to-one, and organized his men in the gyorin (魚鱗, fish-scale) formation, enticing his opponent to attack.

Ieyasu had expected his superior weaponry to overcome Shingen's overwhelming forces and formation, but this assumption was quickly dispelled as Naitō Masatoyo's vanguard cavalry attacked and rapidly overran Honda Tadakatsu's segment of the Tokugawa right.

He brought forward a new set of horsemen from the army's main body, ordering Takeda Katsuyori, Obata Masamori, and Saegusa Moritomo to lead a two-pronged cavalry charge into the weakening Tokugawa line.

In an effort to reorganize his rapidly dissolving army, Ieyasu ordered his commander Ōkubo Tadayo to plant his golden fan standard (uma-jirushi) upon a hill and rally his troops towards the castle town of Saigadake.

Other notable Tokugawa retainers killed in the fighting were Matsudaira Koretada, Naruse Masayoshi, Toyama Kosaku, and Endo Ukon, who all perished as their units were encircled and overrun by the Takeda forces.

When the Takeda vanguard led by Baba Nobuharu and Yamagata Masakage heard the drums and saw the braziers and open gates, they mistakenly assumed that Ieyasu had planned a trap and stopped to made camp for the night at their present position short of Hamamatsu.