 Tactical doctrine determined in 1938 that the Type 91 aerial torpedo should be released at a distance of from the target.As well, the Japanese Navy developed night attack and massed day attack doctrine, and coordinated aerial torpedo attacks between land- and carrier-based torpedo bombers.The Japanese divided their bomber squadrons into two groups so they could attack an enemy battleship from both frontal quarters and make it difficult for the target to avoid the torpedoes by maneuvering, and more difficult for it to direct anti-aircraft fire at the bombers.