In December 1941, Buffalos operated by both British Commonwealth (B-339E) and Dutch (B-339C/D) air forces in South East Asia suffered severe losses in combat against the Japanese Navy's Mitsubishi A6M Zero and the Japanese Army's Nakajima Ki-43 "Oscar". The British attempted to lighten their Buffalos by removing ammunition and fuel and installing lighter guns to improve performance, but it made little difference. After the first few engagements, the Dutch halved the fuel and ammunition load in the wings, which allowed their Buffalos (and their Hurricanes) to stay with the Oscars in turns.