Australia was one of the first nations to commit units to the fighting, playing a small but sometimes significant part in the UN forces, which was initially led by General Douglas MacArthur. Volunteer soldiers deployed in Japan as part of the British Commonwealth Occupation Force (BCOF) formed the basis of the Australian response, with P-51 Mustang fighter-bombers from No. 77 Squadron RAAF flying their first missions on 2 July, while the frigate and the destroyer were also committed to naval operations. During this time the 3rd Battalion, Royal Australian Regiment (3 RAR), which had been preparing to return to Australia prior to the outbreak of the war, remained in Japan, however on 26 July the Australian government announced that it would also commit the under-strength and poorly equipped infantry battalion to the fighting, following a period of preparation. Training and re-equipment began immediately, while hundreds of reinforcements were hastily recruited in Australia as part of K Force; they soon began arriving to fill out the battalion. The battalion's commanding officer, Lieutenant Colonel Floyd Walsh, was replaced by Lieutenant Colonel Charles Green. An officer with extensive operational experience fighting the Japanese in New Guinea during the Second World War, Green took over from Walsh due to the latter's perceived inexperience.