During February 1966, as part of an American road-building program designed to challenge the Viet Cong's ability to manoeuvre in the areas around Saigon, the US 1st Engineer Battalion—under the command of Lieutenant Colonel Howard Sargent—had been engaged in constructing an all-weather road between Route 13 and Route 15 in central Binh Duong Province, west of Ben Cat, on the northern apex of the Viet Cong base area known as the Iron Triangle. This road was planned to cut the communist supply routes between War Zone C, the Mekong Delta, the Iron Triangle and War Zone D, while it would also link the two forward brigades of the US 1st Infantry Division between Phuoc Vinh and Lai Khe and help to extend the authority of the South Vietnamese government.
In response to the American moves, Viet Cong Local Force elements began harassing the sappers, subjecting them daily to sniping, mines and sabotage in an effort to hamper construction. A large American security operation known as Operation Rolling Stone was subsequently launched by elements of US 1st Division on 11 February, in an area of operations around the Suoi Bong Trang, a major creek 30 kilometres (19 mi) north-west of Bien Hoa airbase. The US 1st Brigade under the command of Colonel Edgar N. Glotzbach was allocated the task, and he assigned one of his three battalions to guard the engineers on a rotating basis, while the other two would probe the Viet Cong positions nearby in order to keep them off balance.
Meanwhile, following a request from the American divisional commander, 1 RAR—under the command of Lieutenant Colonel Alex Preece—was detached from the US 173rd Airborne Brigade and placed under the operational command of the US 1st Division until 5 March. Major General William E. DePuy had selected the Australians specifically because of their reputation for dispersed, aggressive patrolling. Attached supporting the infantry from 1 RAR were Australian M113s from 1 APC Troop, engineers from 3 Field Troop, Bell Sioux light observation helicopters and Cessna 180 fixed-wing aircraft from 161st Independent Reconnaissance Flight, and 105-millimetre (4.1 in) L5 Pack Howizters from 161st Battery, Royal New Zealand Artillery.
Headquarters US 1st Brigade was located about 1,000 metres (1,100 yd) east of the engineer base camp in the vicinity of the hamlet of Tan Binh, just north of the new roadway and less than 5 kilometres (3.1 mi) west of Route 16. Meanwhile the battalions of the brigade widely dispersed carrying out search and destroy operations throughout the area of operations, and as such it was only lightly defended. Yet other than the harassment faced by the engineers, contact between the Americans and the Viet Cong had been infrequent during the first weeks of the operation. While details on the location of Viet Cong Main Force regiments was typically limited, Australian intelligence assessed that a minimum of two Local Force platoons, and possibly a Local Force company, were operating in the area but cautioned that the Viet Cong probably had the ability to concentrate a Main Force battalion in the area with little warning. The concept of operations required the Australians to protect the engineer base, the laterite pit and road work parties over a distance of 6,000 metres (6,600 yd), as well as protecting engineer reconnaissance parties when they moved forward to plan new sections of the road.
1 RAR was inserted by helicopter on 19 February, taking over from 2nd Battalion, US 38th Infantry Regiment. Preece immediately instituted a program of twenty-four hour dispersed patrolling, and within two days this succeeded in reducing the level of Viet Cong activity against the road construction. Two platoons of American M48 Patton tanks were also moved into the area, patrolling by day with the Australian armoured personnel carriers, while securing the laterite pit at night. However, by 22 February the Australians noted that in several contacts they were now facing Main Force elements, indicating the possibility of a major communist attack. In the early morning of 23 February three Viet Cong soldiers were killed in an Australian ambush, while several others were wounded but escaped. The dead soldiers were well-equipped with new AK-47 assault rifles and webbing, and they were identified as being from 761st Main Force Regiment. Also captured was a large quantity of ammunition, rations and medical supplies. Later that night a North Vietnamese engineer officer was also killed in a separate ambush, adding further weight to the Australian suspicions. As dawn broke the next day, two half-platoon ambushes from B Company, 1 RAR—under the command of Major Ian McFarlane—engaged two squads of Viet Cong Main Force. Preece immediately warned Glotzbach of an imminent attack, and then informed Sargent that the Australians were moving to set up a defensive position, recommending that the engineers relocate in order to join them.
Meanwhile to the west, three battalions of Viet Cong 9th Division were massing for a decisive blow, preparing a regimental attack on the American and Australian positions. Units identified included J10 Battalion of the 761st Regiment, 707 Battalion of the 763rd Regiment and D800 Independent Battalion; in total around 2,000 men. By 20:00 they had completed a 25 kilometres (16 mi) approach march and were in assembly areas near the village of Ap Bo, using local women and youths as porters to carry ammunition, equipment and supplies. Small reconnaissance parties moved forward as pathfinders, easily locating the American headquarters due to the large amount of noise and light it gave off. The Viet Cong regimental commander determined to attack on three separate axes from the east, and to then send a force around behind the Brigade Headquarters and assault from the west, thereby surrounding the defenders and preventing them from concentrating their forces in defence. Fire support was provided from two separate locations: with 60-millimetre (2.4 in) mortars deployed to the west, in between the Australians and Brigade Headquarters, while 82-millimetre (3.2 in) mortars would fire from a position in Ap Bo to the south-east.
Night assault, 23/24 February 1966Edit
By late afternoon on 23 February 1 RAR had adopted a position in all-round defence in the vicinity of the Suoi Bong Trang, west of Brigade Headquarters, while the US engineers had moved into a new defensive position inside the Australian perimeter. Meanwhile, alerted by the Australians, a platoon of M48 Patton tanks from Troop B, 1st Squadron, US 4th Cavalry Regiment and a second 105-millimetre (4.1 in) howitzer field battery from 1st Battalion, US 5th Artillery Regiment had been moved in to defend the Brigade Headquarters. 1st Battalion, US 26th Infantry Regiment—under the command of Lieutenant Colonel Y.Y. Phillips—returned from the field and also deployed in defence by last light, augmenting Company B, 1st Battalion, US 28th Infantry Regiment. Additional ammunition was also brought forward, in anticipation of a likely Viet Cong attack.
At 22:00, soldiers from B Company, 1 RAR, occupying the western sector of the Australian perimeter noticed lights 250 metres (270 yd) to their front. McFarlane subsequently requested artillery and mortar fire to target the location, but the request was declined by Preece. Meanwhile a small Australian standing patrol, deployed forward of the company main defensive position, and under the commander of Private Walter Brunalli, had observed the lights moving closer, east of Brigade Headquarters. Two tanks had been positioned forward of the American positions, with a squad of infantry on the eastern approaches, and by midnight they had also reported sounds of movement and intermittent flashes of light through the trees. In the early morning of 24 February, just after midnight, sporadic firing was heard throughout the area. The forward American listening posts had detected small groups of Viet Cong moving outside the perimeter, killing two and forcing the remainder to withdraw into the darkness after one of the sentries opened fire. Glotzbach waited for the Viet Cong main effort however, and withheld the bulk of the firepower at his disposal.
With their defences alerted, the Americans and Australians stood to for the next 45 minutes. The battle began at 01:45 with a heavy barrage of Viet Cong mortar and small arms fire. The Americans responded with small arms, machine-guns, tank fire, mortars and artillery and over the next hour the firing grew in intensity until, at 03:00, the Viet Cong switched their fires to the north-west side of the American perimeter, augmenting their fire with recoilless rifles. Glotzbach expected a full-scale ground assault, but the Viet Cong had been held back by the weight of American firepower, with heavy artillery including 8-inch (200 mm) and 175-millimetre (6.9 in) howitzers firing in support from Phuoc Vinh, in addition to the defender's own artillery which was now firing over open sights after lowering their tubes to fire directly at the Viet Cong positions. In total eight field batteries were available. Elsewhere, the Australian standing patrol had remained in position despite the proximity of the Viet Cong, and with the Americans pouring massive fire into the area they were soon caught in the crossfire. Brunalli was subsequently wounded in the arm.
Although the Australian position was not the focus of the attack, it too soon came under attack from 60-millimetre (2.4 in) mortars, killing an American sapper. With the base plate positioned between the Australians and Brigade Headquarters there was initial confusion over the source of the rounds, and both Gloztbach and Preece accused the other of firing on their positions. However, with US aircraft arriving overhead to illuminate the battlefield the Australians were able to join the fighting, and they began firing at masses of Viet Cong seen milling around in the confusion. Earlier, a number of Australian ambushes had intercepted Viet Cong pathfinder groups and this had largely prevented the communists from conducting a final reconnaissance of their objectives. Unaware of the newly strengthened defences they had assaulted into the combined firepower of two American field artillery batteries firing over open sights, as well as tanks supported by infantry. Using anti-personnel canister, flechette and splintex rounds, as well as prepositioned banks of Claymore mines, the Americans broke up several assaults with heavy casualties, while the Australians poured small arms fire into the flank of what was now turning into a costly and futile attack.
Viet Cong withdraw, 24 February 1966Edit
At 02:45 three Viet Cong soldiers had moved to within 25 metres (27 yd) of Brunalli's standing patrol, taking up firing positions. The Australians killed one and wounded another who was dragged away by the third, before they withdrew to another location nearby. Meanwhile, the two American tanks forward of Brigade Headquarters were overrun and their crews killed. Having suffered heavy losses, by 04:00 some of the Viet Cong began to retreat from the battlefield, and many were now filtering past 1 RAR. As groups of Viet Cong began to move past their position the standing patrol was now in an untenable position, clashing briefly with one group of 15 Viet Cong. McFarlane finally ordered the patrol to withdraw, so that he could engage with artillery and mortars. Moving to achieve a clean break, the patrol engaged another group of 10 Viet Cong with a volley of small arms fire, before withdrawing 30 metres (33 yd) towards the company position in the darkness. Expecting to be followed up the Australians set up a snap ambush, killing another Viet Cong soldier before successfully completing the move back to their perimeter.
With the Viet Cong line of withdrawal carrying them past the Australian position, heavy fire was maintained on them as they attempted a partial retreat, resulting in further casualties. However, as daybreak neared the Viet Cong seemed unwilling to commit to an all-out attack, nor to completely withdraw. Finally, the main Viet Cong attack began at 05:30; earlier losses had been heavy, however, and they were unable to mount a massed assault. Instead only a series of disjointed attacks followed, with none more than 40 men strong. By 06:45 all attacks had been repelled by the Americans and the Viet Cong withdrew before dawn, avoiding the arrival of additional American air support.
At first light the next morning Australian clearing patrols located 89 dead and 11 wounded Viet Cong in front of their positions, the bulk of which had been killed by the Americans.[note 1] Countless others had simply been disintegrated by artillery and tank fire and the battlefield was littered with shattered human remains, severed limbs, and chunks of flesh, while red pulp covered the rubber trees that were still standing. Later, 154 bodies were bulldozed into a B-52 bomb crater nearby, while it was estimated that a further 200 Viet Cong casualties had been removed from the battlefield. 15 Viet Cong had also been captured during the battle, as had a large quantity of equipment, including small arms and ammunition, crew-served weapons and grenades. The villagers of Ap Bo were again used by the Viet Cong to carry many of the dead and wounded from the battlefield with ox carts, and they also suffered a number of casualties from artillery and mortar fire landing in the area. In contrast, American casualties were 11 killed and 72 wounded, while Australian casualties were lighter still, with just two men wounded. One American tank had also been destroyed, while two tanks and four armoured personnel carriers were damaged. Overall, the combined US-Australian force had won an impressive victory. However, with the defenders exhausted and with ammunition running low, Glotzbach cautiously decided not to pursue the withdrawing force. Instead the Americans and Australians focussed on securing the battlefield and evacuating their own casualties.
For the next two days, the Australians continued to provide protection to the US engineers before being replaced by an American infantry battalion. 1 RAR subsequently flew out on 26 February, returning to Bien Hoa airbase. Meanwhile, following their repulse at Tan Binh the Viet Cong attempted to avoided further contact, choosing instead to harass the American work parties with occasional mortar and sniper fire. These tactics proved ineffective however, and although the Americans lost a further three killed and 29 wounded, the road was complete by 2 March. The Americans launched an extensive civic action program in an attempt to consolidate their gains, repairing damaged houses, distributing food and providing basic health care to the local population. Despite such efforts though, American commanders were pessimistic about the possibility of achieving any long term gains in Binh Duong Province unless the South Vietnamese Army was able to provide lasting protection for the local population. On 7 March, just five days after the completion of Operation Rolling Stone, the US 1st Brigade was redeployed with US 173rd Airborne Brigade and 1 RAR on Operation Silver City, sweeping the southwest sector of War Zone D.
At the strategic level the ARVN and the South Vietnamese government had both rallied after appearing on the verge of collapse and the communist threat against Saigon had subsided, yet additional troop increases were required if Westmoreland was to adopt a more offensive strategy, with US troop levels planned to rise from 210,000 in January 1966 to 327,000 by December 1966. The Australian government increased its own commitment to the ground war in March 1966, announcing the deployment of a two battalion brigade—the 1st Australian Task Force—with armour, aviation, engineer and artillery support; in total 4,500 men. Additional Royal Australian Air Force (RAAF) and the Royal Australian Navy (RAN) force elements would also be deployed and with all three services total Australian strength in Vietnam was planned to increase to 6,300 personnel. 1 RAR was subsequently replaced and 1 ATF was allocated its own area of operations in Phuoc Tuy Province, thereby allowing the Australians to pursue operations more independently using their own counter-insurgency tactics and techniques. The task force arrived between April and June 1966, constructing a base at Nui Dat, while logistic arrangements were provided by the 1st Australian Logistics Support Group which was established at the port of Vung Tau.