5 RAR commenced its shakedown operation for its second tour on 1 March after having been in the country for fourteen days. The rifle companies deployed into Area of Operations (AO) Burrinjuck.

The AO chosen was west of the Nui Dat base and included the northern and eastern parts of the rugged Nui Dinh mountain complex. The paddi fields at this time were cemented by the sun and the vegetation on the coastal flats was tinder dry. The thick clumps of thorn covered bamboo proved a formidable obstacle to A. and D. Companies, as they deployed west on foot and into Armoured Personnel Carriers (APC's) into the west of the AO.

The mission of the battalion was to conduct Reconnaissance In Force operations aimed at preventing the movement of enemy forces towards Baria from the west, and thus deny possible base plate positions from which major population centres of Phuoc Tuy Province could be bombarded.

At 0800 hours on 2 March, 105 Field Battery fired an artillery preparation into landing Zone (LZ) Marie prior to a heliborne assault from C. Company from Kangaroo pad at Nui Dat. C. Company had secured the LZ an hour later and by 1000 hours battalion headquarters was complete on the ground followed by B. Company. In the afternoon the companies reported fresh sign of enemy movements and located a 107mm rocket launching site.
Before 2300 hours 3 March, A, C and D Companies had reported contacts in their night ambush positions. These continued through the night until 0800 hours 4 march. Sweeps confirmed that eleven enemy had been killed and numerous wounded. The only Australian casualty was 2nd Lieutenant H. Moyle of 11 Platoon D. Company. A shrapnel wound to the knee sent him home to Australia some weeks later.

The next four days saw the companies continuing their operations with scattered light contact. Both the RAAF Iroquois and the army H13 helicopters flying in support received ground fire. 12 Platoon D. Company killed two local guerrillas in contact at 0655 hours 5 March. By last light on 8 March the battalion, less B. Company, was harboured with a troop of tanks and a troop of APC's. At midnight under a full moon D. Company led the battalion across the open paddi and through the bamboo to the perimeter fence of Phuoc Hoa Long.

Phuoc Hoa Long, nestled under the southern perimeter of Nui Dat base was often infiltrated by the Viet Cong guerrillas on resupply and propaganda missions. An extensive political and military communist infrastructure was also known to exist among the 5,100 villagers. 5 RAR's task was to cordon and search the northern hamlets of the village.

C and D Companies were to form the cordon while A and B Companies were to conduct the search. D Company was led along the dark corridor of trees and banana plantations by 10 Platoon. At 0150 hours heavy firing shattered the stealth of the approach. 10 Platoon reported firing from the Regional Force post at the northern end of the town. At the same time 11 Platoon came under AK47 fire from their right flank. The American Liaison Officer succeeded in stopping the fire as soon as it was realised that 10 Platoon elements had moved into their protective minefield The battery fired continuous illumination for four hours while engineers and infantrymen extracted the causalities from the densely planted minefield. The RAAF "Dust Off" helicopters provided exceptional assistance in evacuating the casualties and assisting in their recovery from the actual minefield. In one instance the Iroquois hovered above the rescue party for forty minutes providing illumination with his landing lights. This was an extremely hazardous operation, as there was the chance of the down blast of the blades detonating more mines. This close support from the RAAF was to become considered normal as the tour progressed. Those killed were 2nd Lieutenant B. Walker, Sergeant B. Smith and Corporal G. Gilbert, all of 10 Platoon. Whilst this extraction was being carried out the rest of the battalion closed the cordon.

A 0730 hours an aircraft fitted with a loud speaker system flew over the village and directed the people to the screening area on the northern outskirts. By 1030 hours the sweep was under way. A and B Companies prodded their way around the myriads of small gardens and pagodas, searching the 263 houses in detail. This type of operation is very exhausting because of the ever present threat of mines, booby traps and snipers.
Concurrently with the search, the screening of the people was being carried out by elements of the Divisional Intelligence Unit, The Australian CA (Civil Affairs) Unit, the Psychological Operations Section with National Field Force and Special Police detachments. During this time 1,700 people were screened of whom eleven were detained as suspected members of the VC infrastructure.

At 1700 hours the battalion returned to Nui Dat.

Operation Quintus Thrust proved that the enemy, mainly guerrillas from the Chau Duc Company, were using the footpads around the base of the mountains as liaison routes and infiltration routes into the capital Baria and Phuoc Hoa Long. These paths came from suspected base areas in the Nui Thi Vai mountains. This was verified later on Operation Twickenham.

The Tigers had been blooded and Quintus had cut her teeth. Every man knew now the enemy and the environment which he would be fighting for the next twelve months. But the success were not without the loss of three fine men who paid the supreme sacrifice. Even at this early stage of the tour it was obvious that the modern soldier of 5 RAR was the same man who fought on the cliffs of Gallipoli, the deserts of Africa, and the Jungles of New Guinea.