Australian combat forces were further reduced during 1971. The Battle of Long Khánh on 6–7 June 1971 took place during one of the last major joint US-Australian operations, and resulted in three Australians killed and six wounded during heavy fighting in which an RAAF UH-1H Iroqouis was shot down. On 18 August 1971, Australia and New Zealand decided to withdraw their troops from Vietnam; the Australian prime minister, William McMahon, announced that 1 ATF would cease operations in October, commencing a phased withdrawal. The Battle of Nui Le on 21 September proved to be the last major battle fought by Australian forces in the war, and resulted in five Australians killed and 30 wounded. Finally, on 16 October Australian forces handed over control of the base at Nui Dat to South Vietnamese forces, while the main body from 4 RAR—the last Australian infantry battalion in South Vietnam—sailed for Australia on board HMAS "Sydney" on 9 December 1971. Meanwhile, D Company, 4 RAR with an assault pioneer and mortar section and a detachment of APCs remained in Vũng Tàu to protect the task force headquarters and 1 ALSG until the final withdrawal of stores and equipment could be completed, finally returning to Australia on 12 March 1972.