Other than the North American A-36 Apache, a P-51 modified with dive brakes, the Americans and British used no dedicated CAS aircraft in the Second World War, preferring fighters or fighter-bombers that could be pressed into CAS service. While some aircraft, such as the Hawker Typhoon and the P-47 Thunderbolt, performed admirably in that role, there were a number of compromises that prevented most fighters from making effective CAS platforms. Fighters were usually optimized for high-altitude operations without bombs or other external ordnance – flying at low level with bombs quickly expended fuel. Cannons had to be mounted differently for strafing – strafing required a further and lower convergence point than aerial combat did.