Battle of Long Khanh The Battle of Long Khanh ( 6 – 7 June 1971 ) was fought during the Vietnam War between elements of 1st Australian Task Force ( 1 ATF ) and the Viet Cong and North Vietnamese Army during Operation Overlord . The fighting saw Australian infantry from 3rd Battalion , Royal Australian Regiment ( 3 RAR ) attack a heavily fortified communist base camp in Long Khanh province , while Centurion tank s providing close support crushed many bunkers and their occupants . Regardless , the Viet Cong fought hard to delay the Australian advance and although the bunker system was subsequently captured , along with a second system further south , the Australians suffered a number of casualties and the loss of a UH - 1 Iroquois helicopter . With the Australians unable to concentrate sufficient combat power to achieve a decisive result , the bulk of the communist force successfully withdrew intact , although they likely sustained heavy casualties in the process . Background . As a consequence of the overall allied strategy of Vietnamization and with the Australian government keen to reduce its own commitment to the war , 8 RAR was not replaced at the end of its tour of duty in December 1970 . 1 ATF was again reduced to just two infantry battalions , albeit with significant armour , artillery and aviation support remaining . The Australian area of operations ( AO ) remained the same however , with the reduction in forces only adding further to the burden on the remaining battalions . Regardless , following a sustained effort by 1 ATF in Phuoc Tuy Province between September 1969 and April 1970 , the bulk of communist forces had become inactive and had left the province to recuperate . Accordingly the Australians shifted focus , turning their attention to denying the Viet Cong the chance to resupply by close ambushing around villages and towns , such as Dat Do and Hoa Long . Although not always successful , such operations yielded significant results and by the end of 1970 South Vietnamese forces were increasingly responsible for the security of major population centres . Indeed , the major battles of earlier years were now seen as a thing of the past in Phuoc Tuy . However in May 1971 , following a request from Brigadier Bruce McDonald — the task force commander — the Australian AO was extended a further north across the border into Long Khanh Province . Several reconnaissance patrols from the Special Air Service Regiment ( SASR ) were subsequently inserted in the vicinity of the Courtenay rubber plantation , and later on the other side of Route 2 . These patrols were highly successful , detecting the presence of a substantial communist force , while a number of Viet Cong were also killed . Prelude . Intelligence reports in June , in conjunction with the invaluable information gathered by the SASR , located D445 VC Battalion and 3 / 33 NVA Regiment east of Route 2 along the border between Phuoc Tuy and Long Khanh in an area north of the Australian base at Nui Dat . These reports indicated that the communists were attempting to disrupt the continuing pacification program , and were also using the area to rest , retrain and refit . In response the 1 ATF commander , Brigadier Bruce McDonald , launched a brigade - sized ' search and clear ' operation , known as Operation Overlord . Named after the D - Day landings during the Allied invasion of Normandy in 1944 , the operation was scheduled to begin on the same day , 27 years later . Notably , there was some trepidation among the Australian sub - unit commanders with the use of this name for operational security reasons , as it was felt that it might telegraph their intentions . The concept of operations called for a significant blocking force to be inserted , with 4 RAR / NZ ( ANZAC ) deployed along the line of Suoi Ran river , A Squadron , 3rd Cavalry Regiment to their west and 2 / 8th Battalion , 3rd US Cavalry Regiment to the north - east . Meanwhile , 3 RAR — under the command of Lieutenant Colonel Peter Scott — and the Centurion tanks from C Squadron , 1st Armoured Regiment were tasked with driving the communists into these positions . A number of fire support base s would be established , with A Field Battery and 104 Field Battery , Royal Australian Artillery providing indirect fire support in conjunction with American gunners , while 3 RAR would search its AO — belatedly designated as AO Gwenda — with three rifle companies ( A , B , and C ) , while D Company would be held in reserve . The plan envisioned movement by road of both troops and equipment using Route 2 , as well as air insertion . The terrain in the new AO was thickly wooded with some areas of secondary growth beneath the high canopy , as well as numerous water courses , spurs and re - entrants . Battle . The operation commenced on 5 June with the insertion of the blocking force , followed by the aerial insertion of 3 RAR . The Landing Zone ( LZ ) was clear of large trees to about and was secured by the APCs from A Squadron . As A Company landed it was suddenly engaged by intense fire , which also targeted the unsecured B Company LZ to the south - west . The firing eased after a few minutes however , thereby allowing the insertion of the remaining companies . The Australians subsequently began patrolling and it soon became apparent that they had been dropped within of an extensive bunker system . Signs of a strong communist presence were detected almost as soon as 3 RAR began its sweep , while the blocking elements also had a number of sightings , and a few contacts with small parties moving north . Possibly alerted by allied air and road movements , the communists seemed to be avoiding open combat . Late on the afternoon of 6 June 5 Platoon , B Company located what was thought to be the main communist position , however with nightfall approaching , it was decided not to press the attack that night . During the evening a few shots were exchanged between the Australians and Viet Cong , and the Australian platoon subsequently withdrew into a night harbour . At 06 : 00 artillery commenced bombarding the position , and following a half - hour of preparation , 5 Platoon resumed its advance expecting the communists to have vacated the position during the night , as they had done numerous times in the past . After having only proceeded only , however , the Australians came under heavy fire from the front and both flanks , suffering several casualties in the initial volleys . It soon became apparent that the platoon was pinned down on the edge of a strongly defended and well - concealed bunker system , with the platoon commander calling for assistance from helicopter gunships , as well as indirect mortar fire rather than risking further casualties by withdrawing . Moving to support the platoon in contact , Scott ordered D Company to conduct an assault against the flank and rear of the bunker complex , mounted in APCs with tanks in support . Two troops of Centurions spearheaded the assault through the jungle from the north , and they soon began receiving heavy small arms fire and rocket - propelled grenades , one of which subsequently suffered external damage . Realising that the bunker system was larger than previously estimated , the tanks were forced to halt while the infantry were brought up to begin the assault . Meanwhile , 5 Platoon was in dire straits and was beginning to run low of ammunition , while a number of its M60 machine - guns were also beginning to fail because of the prolonged firing . Moving to outflank the heavily outnumbered Australians , Viet Cong were observed emerging from their bunkers . Indeed only heavy indirect fire and effective suppressing fire from helicopter gunships prevented them from being overrun . Attempting to gain a better position to direct the fire , the B Company Forward Observer moved forward to 5 Platoon , and was killed almost immediately . However by 09 : 15 the remainder of B Company was able to link up with the beleaguered platoon , and after an aerial resupply of ammunition , stabilised the situation temporarily . At 11 : 00 , however , a second attempt to resupply B Company resulted in an Australian Iroquois helicopter being shot down by heavy ground fire , and exploding on impact . Two crew members were killed and another two injured , while another soldier was injured on the ground . With ammunition exploding among the burning wreckage a number of Australians rushed to aid the injured , scrambling through the debris and removing the unexploded ammunition and pulling the survivors to safety . Subsequently another winch point was established to the rear of the Australian positions for casualty evacuation and resupply . By mid - afternoon , D Company had finally moved into position and commenced an assault , pushing through the bunker system from the north - east with the Centurion tanks in close support crushing many bunkers and their occupants with their tracks . The progress of the Australian assault was slowed by thick vegetation and the size of the position , even as the resistance slackened and volume of fire diminished . Indeed the bunker system was later found to cover nearly a square kilometre and was wider than the front of the assaulting company . Painstakingly the Australians searched each bunker systematically . With the action now over , D Company and the tanks subsequently linked up with B Company and established a night defensive position . During the final assault , C Company , located to the south , had uncovered a second bunker system which was subsequently captured by the Australians after being hastily abandoned . More than 16 , 000 rounds of M60 ammunition had been fired during the fighting , along with 6 , 000 rounds of M16 ammunition . The artillery had fired over 1 , 453 rounds of 105 mm and 200 rounds of 155 mm high explosive in support . Over the next six days Australian pioneer and engineer demolition teams proceeded to destroy the remaining bunkers . Aftermath . Despite significantly underestimating the size of the position they faced , the Australians had succeeded in the pushing D445 VC Battalion and 3 / 33 NVA Regiment out of a valuable base area intended for long - term use . Regardless , there were few other tangible results to show for the casualties they had incurred as , although numerous blood trails and body parts scattered around the battlefield indicated that communist casualties had been heavy , the majority of their dead had either been removed from the battlefield or were entombed in the bunkers that had been crushed by the Australian tanks . The battle had cost the Australians three killed and six wounded , while only five Viet Cong bodies were recovered . The communists had defended strongly in order to allow an orderly evacuation of personnel and stores , and with the Australians unable to concentrate sufficient combat power rapidly enough to ensure a decisive result , they were largely able to achieve this objective . Unfazed by the loss of their base - camps , the bulk of the communist force remained intact and later carried out a highly successful ambush by 274 VC Main Force Regiment on 12 June . Seven Australians were killed and three wounded from the HQ 1 ATF Defence and Employment Platoon in this subsequent action , with the bulk of the casualties occurring when an RPG - 7 exploded on a box of M18A1 Claymore mines sitting atop an M113 Armoured Personnel Carrier , igniting them with catastrophic consequences . Operations in Long Khanh continued however , and the Australians established a number of ambushes on possible withdrawal routes , although little contact subsequently occurred . Operation Overlord finally ended on 14 June and 1 ATF returned to Nui Dat . Overall , despite the heavy contact experienced early on , it had yielded little for the Australians although neither D445 or 33 NVA Regiment were encountered in Phuoc Tuy again . Overlord was one of the larger task force operations of the war , while it was also the last joint US - Australian battalion - sized operation . Indeed although the fighting continued , Australian operations began to wind down . On 18 August 1971 , Prime Minister William McMahon announced that 1 ATF would cease operations in October , commencing a phased withdrawal . Ultimately , the last Australian forces were withdrawn from Vietnam by 1973 .