However , with the security situation in South Vietnam continuing to deteriorate , the US increased its involvement to 200 @,@ 000 combat troops by early 1965 . Australia also committed ground forces , dispatching the 1 RAR to serve with the US 173rd Airborne Brigade in Bien Hoa province in June 1965 and it subsequently fought a number of significant actions , including Gang Toi , Operation Crimp and Suoi Bong Trang . In March 1966 , the Australian government announced the deployment of a brigade @-@ sized unit — the 1st Australian Task Force ( 1 ATF ) — to replace 1 RAR . Included were a large number of conscripts , under the increasingly controversial National Service Scheme . Consisting of two infantry battalions as well as armour , aviation , artillery and other support arms , the task force was assigned primary responsibility for its own area and was based at Nui Dat , in Phuoc Tuy Province . Included were the Iroquois helicopters of No. 9 Squadron RAAF . At the Battle of Long Tan on 18 August 1966 , D Company , 6 RAR with considerable artillery support held off and defeated a Viet Cong force that was at least six times bigger than itself . 18 Australians were killed and 24 wounded , while 245 communist dead were later recovered from the battlefield . The battle allowed the Australians to gain dominance over Phuoc Tuy Province and 1 ATF was not fundamentally challenged again . Regardless , during February 1967 the Australians suffered their heaviest casualties in the war to that point , losing 16 men killed and 55 wounded in a single week , the bulk during Operation Bribie .