 The highway to Xuyen Moc in the east had been reopened by the Australians in March and April , and with the Viet Cong 275th Regiment believed to have been severely weakened following Long Tan , a series of operations aimed at destroying the Viet Cong 274th Regiment were subsequently launched by 1 ATF . Australian assessments of the Viet Cong 275th Regiment were seemingly reinforced by its unsuccessful attempt to ambush a convoy from US 11th Armoured Cavalry Regiment ( 11 ACR ) on 2 December 1966 . Meanwhile , after Westmoreland had again pressed Vincent on what he saw as the limited results achieved by Australian tactics , a large joint US @-@ Australian operation was mounted against the May Tao mountains in Phuoc Tuy , moving against the communist bases in the area . The largest search and destroy operation mounted by the Australians to that point , Operation Paddington ( 9 – 15 July ) was carried out in co @-@ operation with American and South Vietnamese units based in Bien Hoa province , and targeted the Viet Cong 5th Division . 
