He took part in the Battle of Komaki and Nagakute in 1584, where he was a general commander of the detached surprise attack force in Mikawa Province for 'intermission,' but they suffered terrible defeat by a surprise attack by the Ieyasu TOKUGAWA army; Hidetsugu lost Tsuneoki IKEDA, his father-in-law along with Nagayoshi MORI, and escaped with his bare life.
天正12年（1584年）の小牧・長久手の戦いにも参加し、このとき「中入り」のため三河国別働奇襲隊の総指揮を執ったが、逆に徳川家康軍の奇襲を受けて惨敗し、舅である池田恒興や森長可らを失い、命からがら敗走する。