Early combat operations pointed to the need for more armor and self-sealing fuel tanks, which were included in the P-40B (called the Tomahawk Mk IIA in the UK). These improvements came at price: a significant loss of performance due to the extra weight. Further armor additions and fuel tank improvements added even more weight in the P-40C (Tomahawk Mk IIB). Curtiss addressed the airplane's mounting performance problems with the introduction of the P-40D (Kittyhawk Mk I), which was powered by a more powerful version of the Allison V-1710 engine, and had two additional wing-mounted guns. The engine change resulted in a slightly different external appearance, which was the reason the RAF renamed it from the Tomahawk to the Kittyhawk. Later, two more guns were added in the P-40E (Kittyhawk Mk IA), and this version was used with great success by General Claire Chenault's American Volunteer Group (The Flying Tigers) in China. Some additional models, each with slight improvements in engine power and armament, were the P-40F (with a 1300 hp Rolls-Royce Merlin engine), the P-40G, P-40K (Kittyhawk Mk III), P-40L, P-40M and finally, the P-40N, of which 5200 were built (more than any other version.) While it was put to good use and was certainly numerous in most theaters of action in WWII, the P-40's performance was quickly eclipsed by the newer aircraft of the time, and it was not considered one of the "great fighters" of the war | 
