Battle of Mikatagahara
According to the Kansei Chōshū Shokafu, a genealogy of major samurai by the Tokugawa shogunate, Hattori Hanzō rendered meritorious service during the Battle of Mikatagahara, he captured a Takeda spy named Chikuan, and counterattacked Takeda's troops with only thirty men at the Tenryū River.