Terumasa Ikeda was born in Harima Province, territory of the Ikeda clan. He fought for the Toyotomi like his father, Tsuneoki Ikeda, did, and Tsuneoki fell at the Battle of Komaki-Nagakute when his son was nineteen. Terumasa fought in the Fall of Odawara alongside Hideyoshi Hashiba, his father's master, and gained great traits as a fighting commander. In 1598, after the death of Hideyoshi, Terumasa joined an Anti-Ishida Coalition led by Masanori Fukushima, that was defeated at the Battle of Kyoto. Two years later, ironically, he bowed to the Tokugawa and led a unit into battle at Sekigahara, and was allowed to retain control over Harima. He died in the capital, Himeji Castle.