In June 1575, Katsuyori TAKEDA who was furious at the breakaway of the Okudaira clan marched towards Nagashino-jo Castle with his massive army of 15,000 men.
奥平氏の離反に激怒した武田勝頼は、天正3年5月（1575年）に1万5000を号する大軍を率いて長篠城へ押し寄せた。