Operation Hammersley was undertaken between February and March 1970 in the Long Hai hills of Phuoc Tuy Province, South Vietnam. The hills were a refuge for local Viet Cong, and took advantage of the terrain to escape air strikes and evade Australian patrols.
On 10 February 1970 a combined force of Australian infantry, tanks, armoured personnel carriers (APCs), mortars and combat engineers entered the foothills and clashed with the Viet Cong. RAAF helicopters flew in support of the ground forces while offshore a Royal Australian Navy destroyer was positioned to provide gunfire support.
Five days later, on 15 February, an Australian platoon ambushed a company sized group of Viet Cong and a pitched battle quickly developed as artillery and mortar fire was called upon.
On 16 February Australian infantry, supported by tanks and APCs, began combing the hills seeking survivors from the previous day's fighting. Two days later Australian troops advanced against well-concealed, heavily-fortified Viet Cong bunkers.
Artillery and helicopters added to the weight of firepower arrayed against the enemy. The tanks came under heavy fire and a ferocious fight ensued as the Australians tried to extricate themselves.
The Australians maintained a tight cordon to prevent the enemy slipping away and waited to resume the attack in the morning. Wary of incurring heavy casualties, senior commanders decided a B-52 strike was needed to clear the area. However, this did not destroy the Viet Cong, who had retreated when the Australians pulled back in preparation for the air strike, which was not launched until several days later. Mines were a particular danger in the area and caused many Australian casualties. 28 February was the worst day for mine casualties in Australia's war in Vietnam, with eight men killed and 15 wounded (one fatally) on that day.
In total, over 70 Australians were killed or wounded during the operation.