This structure helped the gate door to be in a blind spot in an attack, and in many battles of the Boshin War at the end of Edo period, they were successful in preventing the New Government Army from breaking through Kita demaru Ottemon gate, allowing the castle to be held for a long time.
この構造は門扉が砲撃の死角となるようにできており、幕末戊辰戦争では緒戦において北出丸の追手門を突破しようとした新政府軍の阻止に成功し、長期籠城戦に持ち込んだ。