the Battle of the Bismarck Sea, imported Bristol Beaufighters proved to be highly effective ground attack and maritime strike aircraft. Beaufighters were later made locally by the DAP. Although it was much bigger than Japanese fighters, the Beaufighter had the speed to outrun them. The RAAF's heavy bomber force predominantly comprised 287 B-24 Liberators, which could bomb Japanese targets as far away as Borneo and the Philippines from airfields in Australia and New Guinea. In September 1942 most Australian squadrons were grouped under RAAF Command. The only Australian air combat units in the SWPA not under RAAF Command were those based in New Guinea as No. 9 Operational Group RAAF, which was controlled by Fifth Air Force. RAAF Command was charged with defending Australia, except in the north-east, protecting the sea lanes to New Guinea, and conducting operations against Japanese shipping, airfields and other installations in the Dutch East Indies. Its role was thus "mainly defensive" at the outset, with the expectation that "in the event of developments in the North and North-West of Australia, this would be altered". Bostock was to exercise control of air operations through the RAAF area command system, comprising North-Western, Western, Southern, Eastern, and North-Eastern Area Commands. By late 1945, the RAAF had received or ordered about 500 P-51 Mustangs, for fighter/ground attack purposes. The Commonwealth Aircraft Corporation initially assembled US-made Mustangs, but later manufactured most of those used. The RAAF's main operational formation, the First Tactical Air Force, comprised more than 18,000 personnel and 20 squadrons; it had taken part in the Philippines and Borneo campaigns and was scheduled to participate in the invasion of the Japanese mainland, Operation Downfall. So too were the RAAF bomber squadrons in Europe, as part of the proposed Tiger Force. However, the war was brought to a sudden end by the US nuclear attacks on Japan. As a result of the Empire Air Training Scheme, about 20,000 Australian personnel had served with other Commonwealth air forces in Europe during World War II. A total of 216,900 men and women served in the RAAF, of whom 9,780 lost their lives. At war's end, a total of 53 RAAF squadrons were serving in the Pacific and a further 17 in Europe. With over 152,000 personnel operating nearly 6,000 aircraft it was the world's fourth largest air force, after those of the USA, the USSR and the UK. Post-World War II