This movie was released in Japan on December 7, the third anniversary of the attack on Pearl Harbor.
'Bangalore torpedo' (or 'Bangalore mine') was the name given to an explosive charge placed within one or more tubes. Invented in 1912, it could be detonated from a short distance for the purpose of clearing battlefield obstacles. In WWI, these were used primarily to clear barbed wire. These devices, with improvements along the way, were manufactured up until 2017.