The Battle of Suoi Bong Trang (23–24 February 1966) was an engagement fought between US, Australian and New Zealand forces, and the Viet Cong and North Vietnamese Army during the Vietnam War. The battle occurred during Operation Rolling Stone, an American security operation to protect engineers building a tactically important road in the vicinity of Tan Binh, in central Binh Duong Province, 30 kilometres (19 mi) north-west of Bien Hoa airbase. During the fighting, soldiers from the US 1st Brigade, 1st Infantry Division and the 1st Battalion, Royal Australian Regiment (1 RAR), which had been attached for the operation, fought off a regimental-sized Viet Cong night assault. Repulsed by massed firepower from artillery and tanks, the Viet Cong suffered heavy casualties and were forced to withdraw by morning. After the attack, the Americans and Australians made no attempt to pursue the Viet Cong, focusing on securing the battlefield and evacuating their own casualties. The Viet Cong continued to harass the American sappers with occasional sniper and mortar fire, but these tactics proved ineffective, and the road was completed by 2 March.
Background
Military situation
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, laying mines and carrying out 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 approximately 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 to support 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.
Prelude
Opposing forces
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. The brigade's constituent battalions were widely dispersed carrying out search and destroy operations, and the area of operations was only lightly defended. Nevertheless, except for 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 US and Australian forces possessed only limited details regarding the location of Viet Cong Main Force regiments, Australian intelligence assessed that a minimum of two Local Force platoons, and possibly a Local Force company, were operating in the area but cautioned commanders 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.
On 19 February, 1 RAR was inserted by helicopter, 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 had 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. Several contacts took place and by 22 February the Australians began to suspect that a major attack on them was being planned, noting that they were now facing Main Force elements. 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 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-kilometre (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 the US 1st Brigade's headquarters, while 82-millimetre (3.2 in) mortars would fire from a position in Ap Bo to the south-east.
Battle
Night assault, 23/24 February 1966
By late afternoon on 23 February 1 RAR had adopted a position in all-round defence in the vicinity of the Suoi Bong Trang, a major creek to the west of the US 1st Brigade's 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 that had deployed forward of the company main defensive position under the command of Private Walter Brunalli, observed the lights moving closer, east of the US 1st Brigade's 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 barrage 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 defenders' 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 the US 1st Brigade's 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, after US aircraft arrived overhead to illuminate the battlefield the Australians were able to join the fighting, and they began firing at masses of Viet Cong who had become disorientated and were milling around on the battlefield. 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.