On March 9, 1582, the troop led by Katsuyori and his legitimate son, Nobukatsu TAKEDA, was attacked by Nobushige OYAMADA at Sasago-toge Pass (Present-day Otsuki City, Yamanashi Prefecture) just before reaching Iwadono-jo Castle, and was prevented from entering the castle.
3月9日に勝頼とその嫡男の武田信勝一行は岩殿城を目前にした笹子峠（山梨県大月市）で小山田信茂に攻撃され、岩殿城入城を拒まれる。