Fuji River
The battle started when Fukushima Masanori, the leader of the Tokugawa advance guard, charged north from the Eastern Army's left flank along the Fuji River against the Western Army's right centre under Ukita Hideie. The ground was still muddy from the previous day's rain, so the conflict there devolved into something more primal. Ieyasu then ordered attacks from his right and his centre against the Western Army’s left in order to support Fukushima's attack.