The B5M was also given the long formal designation Navy Type 97 Mk.2 Carrier Attack Bomber (Japanese: 九七式二号艦上攻撃機) and Allied reporting name of Mabel.

The machine was to have a crew of three, folding wings for flight deck storage, a speed of not less than 322 km/h (200 mph), a flight endurance of not less than seven hours, and the ability to carry at least 800 kg (1,760 lb) of bombs - a tall order for a single-engine aircraft of the mid-1930s.

Although designed as a carrier-based aircraft, it was relegated to land-based torpedo bomber duties in World War II.

The aircraft that Mitsubishi produced first flew in 1937 and was an all-metal, low-wing cantilever monoplane with fixed undercarriage and large wheel spats.

While they had originally been intended for aircraft carrier use, the majority were employed during the early months of World War II from land bases in Southeast Asia and China, where they were confronted by weak or no enemy fighter opposition.