Battle of Mikatagahara
Ietada was the fourth son of Matsudaira hirotada, who was the head of the Fukōzu branch of the Matsudaira clan. Ietada served his brother Tokugawa Ieyasu from a young age. In 1572, he fought at the Battle of Mikatagahara. He fought in many of Ieyasu's campaigns, including against Takeda Katsuyori. In 1590, Ietada was granted Oshi Domain (100,000 "koku") in Musashi Province. He was transferred to Kashira Domain in 1592 and to Omigawa Domain in 1594.