 Once the F @-@ 111 had been ordered , Hancock sought a suitable forward airfield from which they could operate . In this , he continued a policy initiated by his predecessor as CAS , Air Marshal Scherger , of developing a chain of so @-@ called " bare bases " in Northern Australia . Hancock recommended redeveloping RAAF Base Learmonth in the northern part of Western Australia , due to its proximity to Indonesia . Flying out of this airfield , the F @-@ 111s could destroy " vital centres in Java " ; just as importantly for deterrence purposes , Hancock contended , enhancing the base 's capability would send a clear message to Indonesia 's hierarchy . Though the project was delayed , in part due to thawing in relations between Australia and Indonesia , Learmonth 's upgrade was completed in 1973 , the same year that the F @-@ 111 finally entered RAAF service . The latter part of Hancock 's tour as CAS coincided with the beginning of large @-@ scale Australian involvement in the Vietnam War . By mid @-@ 1964 , the Commonwealth had already sent a small team of military advisors , plus a detachment of newly acquired DHC @-@ 4 Caribou cargo planes , to the region at the request of the South Vietnamese government . Under Hancock , the Caribou had itself only been reluctantly ordered by the Air Force following intense pressure from the Army and the Federal government for an STOL transport . Concerned at the potential drain on the RAAF 's resources , Hancock tried to resist calls for commitments to Vietnam . His negative views were in contrast to the hawkish attitudes of his deputy , Air Vice Marshal Colin Hannah , and Air Chief Marshal Scherger , now Chairman of the Chiefs of Staff Committee and Australia 's senior soldier . In April 1965 , as part of American operations in Indochina , United States Air Force strike aircraft took up residence at Ubon Air Force Base , Thailand , which since 1962 had been home to No. 79 Squadron Sabres and run by the RAAF under SEATO arrangements . Hancock proposed that Australia continue to command the facility and provide local air defence , though this effectively made the Sabres a support unit in the war effort and therefore potential targets of North Vietnamese attack ; in the event , none occurred . 
