The reasons for this include the facts that Mototada TORII, the commander-in-chief, and his troop fought back unexpectedly against the attacking force and that the besieging army had some soldiers who had been forced to join the western army by Mitsunari and some other people and thus had little will to fight.
城将の鳥居元忠とその兵達が予想外の奮戦を見せ、また包囲軍の内部にも三成らに強制的に西軍として与させられた者がおり、戦意が上がらなったなどの要因があったためとされる。