Only five inverted gull wing aircraft were designed before and during World War II: the Junkers Ju 87 “Stuka”, the Vought F4U Corsair, the Mitsubishi A5M “Claude”, the Aichi B7A, and the Blohm & Voss Ha 137. However, only the first three ones were massively produced and widely used during the war. The Stuka and the Corsair became historically famous flying weapons, which played a decisive role in the ferocious battles of WWII.
The Junkers Ju 87 was a German land-based dive bomber, which saw combat action from the beginning of the war, being an important piece in the German Blitzkrieg war machinery, fulfilling the role of flying artillery that provided fire support to front line ground forces. Introduced in late 1942, the American F4U was the best carrier-based fighter aircraft of this armed conflict, but it was used only in the Pacific Theater of operations. The A5M was also a carrier-borne fighter, which had entered service with the Imperial Japanese Navy in 1936, but it was much slower and with a weak fuselage; however, only the prototype of this Japanese fighter had this type of wing.
The aerodynamic advantage of the inverted gull wing in these WWII piston-engine aircraft lay in that the wing-fuselage connection was diagonal (oblique) and, thus, had inherently lower drag than any other connection. Another rationale for designing and building an inverted gull wing aircraft was that it allowed clearance for a larger external bomb load. In the Corsair, it was conceived for propeller clearance, since it had much longer blades due to its powerful engine.