1 ATF deliberately established fire support bases astride the PAVN/VC lines of communication in the vicinity of the village of Trang Bom, expecting that they would attempt to destroy them.

The Australians subsequently clashed with the VC during early patrols in Area of operations (AO) Columbus, while later Fire Support Base (FSB) Andersen was repeatedly subjected to major ground assaults.

Meanwhile, the remaining Australian forces in Phuoc Tuy Province also successfully repelled repeated VC attacks against Bà Rịa and Long Điền, as part of the Tet Offensive that had engulfed population centres across South Vietnam.At 18:00 on 29 January 1968, South Vietnamese forces began a 36-hour ceasefire in celebration of the arrival of the Year of the Monkey.

Earlier, the PAVN/VC had declared a seven-day ceasefire as part of the Tết festival, that was normally a period of truce and for community gatherings and family reunions in Vietnamese society.

[1] However, despite such measures the fighting at Khe Sanh had largely succeeded in diverting American resources and attention away from Saigon and towards the demilitarized zone, affording the PAVN/VC the element of surprise.

[4] Regardless, the offensive proper began in the early hours of 31 January when 85,000 to 100,000 PAVN/VC troops simultaneously assaulted population centres and allied installations across South Vietnam.

[1][2] US and South Vietnamese intelligence reports of the impending attacks had afforded some forewarning, and although failures had caught some allied units unprepared, they did not come as a complete surprise.

[1] Indeed, the growing threat had earlier prompted Lieutenant General Frederick Weyand, commander of III Corps Tactical Zone, to request the use of the 1st Australian Task Force (1 ATF)—now at full strength with three infantry battalions and support arms—outside of their usual base in Phuoc Tuy Province in order to defend the vital bases in the Long Binh–Bien Hoa complex north-east of Saigon.

On that occasion 1 RAR had encountered heavy resistance in a series of bunker systems protecting key VC supply lines at Gang Toi.

[9] As part of the plan to protect these bases a combined US-Australian force would establish a screen to interdict movement along the northern approaches to Long Binh–Bien Hoa.

[10] Only sparsely inhabited, AO Columbus was situated east of Long Binh between Highway 1 to the south, and the Song Dong Nai river to the north.

[13] The Task Force Maintenance Area was subsequently located at Andersen, with 1 ATF re-supplied throughout the operation by elements of 1st Australian Logistic Support Group deployed forward in Long Binh.

[7][17] The Australians began an intensive patrol program in AO Columbus[9] and were soon fighting up to platoon-sized VC units in a series of bunker complexes.

[24][25] With the Tet offensive erupting across South Vietnam, Bien Hoa Air Base received heavy rocket fire that caused extensive damage to buildings, aircraft, and facilities, while the Long Binh Logistics Depot and the prisoner of war camp were also hit.

[24] Between 31 January and 1 February, the Australian battalions moved into company blocking positions and a number of minor contacts occurred, resulting in some VC casualties and the capture of more weapons and equipment.

[24] Indeed, during early February, the nature of contacts in AO Columbus began to change, with the Australians increasingly faced by larger company-sized Main Force units located in static defensive positions.

[27] C Company, 7 RAR had been detached in order to protect the task force headquarters as well as to act as a reserve, and was particularly heavily engaged during this phase.

[30] Elsewhere, Tet had also engulfed Phuoc Tuy Province and although stretched thin the remaining Australian forces there were soon drawn into heavy combat as VC units simultaneously attacked the main provincial towns.

[34] While the Australians in AO Columbus had successfully interrupted the pre-positioning of PAVN/VC forces on one of the main approaches to Saigon, in hindsight they had been deployed too late to interfere seriously with the offensive.

[9] The PAVN/VC barrage had had a devastating effect, falling among the American and New Zealand gun positions, the mortar lines and the battalion echelon, as well as scoring a direct hit on an Australian engineer standing patrol.

[38] As a result of the growing threat to the Australian base, the decision was made to reinforce FSB Andersen, with C Company, 3 RAR flown in by the time of the second attack two nights later.

[38] A clearing patrol later revealed that the VC had inserted a mortar team to the edge of the rubber trees by night in a Lambretta and a cart and had then manhandled the tubes into position.

Prior to Tet American commanders and politicians had talked confidently about winning the war, arguing that Westmoreland's strategy of attrition had reached the point where the PAVN/VC were losing soldiers and equipment faster than they could be replaced.

[51] Tet had a similar effect on Australian public opinion, and caused growing uncertainty in the government about the determination of the United States to remain militarily involved in Southeast Asia.

[52] Amid the initial shock, Prime Minister John Gorton unexpectedly declared that Australia would not increase its military commitment in South Vietnam beyond the current level of 8,000 personnel.

[53] The war continued without respite however, and between May and June 1968 1 ATF was again deployed away from Phuoc Tuy in response to intelligence reports of another impending offensive.

The Australians subsequently took up positions north-east of Saigon during Operation Toan Thang I to interdict PAVN/VC lines of communication, fighting a series of significant actions over a 26-day period that became known as the Battle of Coral–Balmoral.