The North American Aviation Corporation's series of "Lightweight" Mustangs, the XP-51F, XP51G, XP-51J, and ultimately the P-51H, came as a result of North American's further development of their standard P-51A and B/C designs. These efforts were the direct result of combat experience in Europe in attempting to counter the fast German Luftwaffe's Focke Wulf 190 with its higher rate of roll, and the requirement in the Pacific Theater for a light, long-range fighter to counter Japanese aircraft, particularly the long-range, highly-manueverable Mitsubishi A6M Reisen ("Zero" or "Zeke").