At the beginning of war, he attacked Inuyama-jo Castle, and then he attempted to attack Ieyasu's home province of Mikawa together with Hidetsugu MIYOSHI (Hidetsugu TOYOTOMI), Nagayoshi MORI (husband of a Tsuneoki's daughter), and Hidemasa HORI, but he met with a misfortune of receiving a shot in the saddle and falling from a horse during the early part of the war (the misfortune doubled as he let himself become furious and lost freedom to move due to injury), he died in Nagakute together with Nagayoshi.
緒戦で犬山城を攻略したのち、三好秀次（豊臣秀次）・森長可（恒興の娘婿）・堀秀政とともに家康の本拠三河を攻めようとしたが、合戦の前半で鞍に銃弾を受け落馬したことが災いとなり（逆上してしまったことと負傷し身動きの自由を失ったことと二重に災いをなした）長久手にて長可とともに戦死。