Operation Crimp (8–14 January 1966), also known as the Battle of the Ho Bo Woods, was a joint US-Australian military operation during the Vietnam War, which took place 20 kilometres (12 mi) north of Cu Chi in Binh Duong Province, South Vietnam. The operation targeted a key Viet Cong headquarters that was believed to be concealed underground, and involved two brigades under the command of the US 1st Infantry Division, including the 1st Battalion, Royal Australian Regiment (1 RAR) which was attached to the US 173rd Airborne Brigade. Heavy fighting resulted in significant casualties on both sides, but the combined American and Australian force was able to uncover an extensive tunnel network covering more than 200 kilometres (120 miles), at the cost of 8 Australians and 14 Americans killed and 29 Australians and 76 Americans wounded.
The operation was the largest allied military action mounted during the war in South Vietnam to that point, and the first fought at division level. Despite some success, the allied force was only able to partially clear the area and it remained a key communist transit and supply base throughout the war. The tunnels were later used as a staging area for the attack on Saigon during the 1968 Tet offensive before they were largely destroyed by heavy bombing from American B-52 bombers in 1970, ending their utility.
Background
Military situation
Although the initial American commitment to the war in Vietnam had been limited to advice and materiel support, by 1964 there were 21,000 US advisors in South Vietnam. However, with the Army of the Republic of Vietnam (ARVN) weakened by successive defeats at the hands of the communists, the South Vietnamese government faltering, and Saigon threatened with a major offensive, the worsening situation led to a significant escalation of the war in 1965, with a large-scale commitment of US ground troops under the command of General William Westmoreland. At first the Americans had adopted a cautious strategy, applied to the strictly limited role of base defence by US Marine units. This was abandoned in April 1965, and replaced by a new "enclave strategy" of defending key coastal population centres and installations. This strategy required the introduction of nine additional US battalions, or 14,000 troops, to bring the total in Vietnam to 13. Allied nations of the Free World Military Assistance Forces were expected to contribute another four battalions.
Westmoreland planned to develop a series of defensive positions around Saigon before expanding operations to pacify the South Vietnamese country-side and as a result a number of sites close to Viet Cong dominated areas were subsequently chosen to be developed into semi-permanent divisional-level bases. Such areas included Di An which was intended to become the headquarters of the US 1st Infantry Division, while the US 25th Infantry Division would be based in the vicinity of Cu Chi. However, large-scale military operations to clear the intended base areas had to wait until the dry season. Yet the allied enclave strategy proved only transitory and further setbacks led to additional troop increases to halt the losing trend. With the situation reaching crisis point during the Viet Cong wet season offensive in June 1965, Westmoreland requested further reinforcement and US and allied forces increased to 44 battalions which would be used to directly bolster the ARVN.
Australia's growing involvement in Vietnam reflected the American build up. In 1963, the Australian government had committed a small advisory team, known as the Australian Army Training Team Vietnam (AATTV), to help train the South Vietnamese forces. However, in June 1965 the decision to commit ground troops was made, and the 1st Battalion, Royal Australian Regiment—originally commanded by Lieutenant Colonel Ivan 'Lou' Brumfield—was dispatched. Supporting 1 RAR was 1 Troop, A Squadron, 4th/19th Prince of Wales's Light Horse equipped with M-113 Armoured Personnel Carriers, artillery from 105th Field Battery, Royal Australian Artillery and 161st Field Battery, Royal New Zealand Artillery, and 161st Reconnaissance Flight operating Cessna 180s and Bell H-13 Sioux light observation helicopters; in total 1,400 personnel. The Australian and New Zealand units were attached to the US 173rd Airborne Brigade under the command of Brigadier General Ellis W. Williamson in Bien Hoa and operated throughout the III Corps Tactical Zone to help establish the Bien Hoa-Vung Tau enclave. Although logistics and resupply were primarily provided by the Americans, a small logistic unit—1st Australian Logistics Company—was situated at Bien Hoa airbase. Unlike later Australian units that served in Vietnam, which included conscripts, 1 RAR was manned by regular personnel only.
Attached to US forces, 1 RAR would primarily be employed in search and destroy operations using the newly developed doctrine of airmobile operations, utilising helicopters to insert light infantry and artillery into an area of operations, and to support them with aerial mobility, fire support, casualty evacuation, and resupply. The battalion commenced operations in late June 1965 and initially focussed on defeating the Viet Cong's wet season offensive. During this time US 173rd Brigade, including 1 RAR, conducted a number of operations into War Zone D—a major communist base area at the junction of Phuoc Long, Long Khanh, Bien Hoa and Binh Duong provinces—as well as in the Iron Triangle, formed by the confluence of the Saigon and Thi Tinh rivers and Route 7, where they fought a number of significant actions including the Battle of Gang Toi on 8 November. Meanwhile, Brumfield was replaced by Lieutenant Colonel Alex Preece, after an old football injury forced his evacuation to Australia in mid-November. During the period 21 November to 16 December 1 RAR was involved in Operation New Life in the La Nga Valley, 75 kilometres (47 mi) north-east of Bien Hoa in an attempt to deny the Viet Cong access to the rice harvest. On 24 November D Company, 1 RAR carried out a deliberate attack on the fortified village of Duc Hanh which had been occupied by the Viet Cong, killing 10 and wounding four without loss. Operation Marauder on the Plain of Reeds in the Mekong Delta was subsequently launched on New Years Day 1966.
Prelude
Opposing forces
Located 4 kilometres (2.5 mi) west of the Iron Triangle, the Ho Bo Woods were believed to contain the political-military headquarters of the communist 4th Military Region, which controlled all Viet Cong activity around the South Vietnamese capital, Saigon. Although its precise position was unknown, it was believed to be concealed in an extensive underground bunker system. Agents' reports, the interrogation of prisoners, and aerial surveillance all pointed to the presence of this vital communist facility. The headquarters itself was believed to be located in a 31-square-kilometre (12 sq mi) area of jungle and marshland, and to have four entrances guarded by a Viet Cong Regional Force company, while two Main Force battalions were also thought to be in the vicinity to afford additional security. Communist units detected in the Ho Bo Woods by allied intelligence included the C306 Local Force Company, 3rd Quyet Thang Battalion and 7th Cu Chi Battalion. The commander of the Cu Chi Battalion was later identified after the war as Captain Nguyen Thanh Linh. In total, local communist defensive strength was believed to include 1,000 men.
In response, a large American 'search-and-destroy' operation was launched in January 1966, involving more than 8,000 troops commanded by the US 1st Infantry Division under Major General Jonathan O. Seaman, including the US 3rd Infantry Brigade, 1st Infantry Division and the US 173rd Airborne Brigade, which was attached to the division for the operation; in total six battalions plus supporting arms. Still attached to the US 173rd Airborne Brigade was the Australian battalion, 1 RAR—now commanded by Preece—with 105 Field Battery in direct support, as well as engineers from 3 Field Troop, Royal Australian Engineers and the M113s from the Prince of Wales Light Horse. At the time it was the largest military operation mounted in South Vietnam, being the first divisional offensive to date. Preceded by a heavy aerial bombardment, the scheme of manoeuvre envisioned an airmobile assault by the US 173rd Brigade in the north and west, while the US 3rd Infantry Brigade would seal off the area to the south, in preparation for a sweep designed to push trapped communist forces eastwards against the Saigon River. 1 RAR's role was to establish a blocking position in a village beside the river on the northern flank of the brigade's area of operations.
In order to achieve tactical surprise, the operation was launched immediately following Operation Marauder, with the Australians and Americans redeployed by air. Prior to the assault, the 1 RAR Operations Officer, Major John Essex-Clarke, conducted an aerial reconnaissance of the proposed Landing Zone—known as LZ June—on 7 January. Observing a lack of ground foliage, he was concerned about the possibility of extensive Viet Cong defensive works close to the LZ, and with the support of Williamson the landing zone was subsequently switched to a less-exposed location. The original plan would have seen 1 RAR inserted directly on top of a heavily defended bunker system, and would have likely resulted in heavy casualties. Captain Alexander "Sandy" MacGregor, the commander of the 3 Field Troop, was of the opinion that the "decision almost certainly saved hundreds of Australian lives."
Battle
Insertion, 8 January 1966
The battle began at 09:30 on 8 January with heavy American preparatory fire from artillery, as well as napalm and airstrikes from B-52 bombers which resulted in significant defoliation. Soon after the airmobile operation commenced with the first American units being inserted by helicopter to the north, west and south. The US 3rd Infantry Brigade—under the command of Colonel William Brodbeck—was subsequently inserted by helicopter and by road. The brigade headquarters and command element departed Di An in convoy and reached Trung Lap on the western boundary of the brigade's area of operations by midday. Concurrently, two battalions were inserted by helicopter to the south-west, one blocking the south side of the Ho Bo Woods while the other conducted a sweep. The Americans were in contact almost immediately, although the engagements were generally small scale, or involving snipers. Meanwhile, the brigade's third battalion moved by road to Trung Lap and then moved on foot to its assigned search area.
In the north, 1 RAR was inserted into its new landing zone—LZ March—3 kilometres (1.9 mi) to the south-west. With B Company securing the site, the battalion moved on foot to the line of departure but not before they were mistakenly engaged by US helicopter gunships and artillery fire. However, after the Australians established communications, the shelling was halted and they began their advance. No sooner had the lead elements—D Company under the command of Major Ian Fisher—emerged into the cleared area that was originally to have been used as the battalion's LZ, when the forward platoon came under fire from Viet Cong positions in the tree-line on the north-east corner. In the action which followed, six Australians from 12 Platoon were wounded, including platoon commander Lieutenant Jim Bourke, who was shot through the jaw but remained in command until he passed out from loss of blood. Meanwhile, two medics who attempted to move forward to treat the casualties were themselves shot and killed.
Preece moved to push his other companies around each flank of D Company, and towards the battalion's original blocking position. Soon they were also in contact with small groups of Viet Cong from positions behind trees and in bunkers, while others popped up from spider holes and tunnel entrances; it became apparent to the Australians that they had stumbled across a significant Viet Cong force in extensive fortifications, sufficient to hold a battalion. B Company, under the command of Major Ian McFarlane, also uncovered a small dug-in hospital with simple transfusion equipment, documents and bandages. Meanwhile, the remaining battalions of the US 173rd Airborne Brigade had also been inserted. The 1st Battalion, US 503rd Infantry Regiment flew into LZ April at 12:00, while US 2/503rd Battalion arrived at LZ May at 14:30. With the insertion going largely according to plan, the brigades began their advance eastwards. Converging on the suspected location of the communist headquarters, a thorough search of the area yielded little, and it was believed that the Viet Cong had withdrawn earlier in response to the initial Australian advance.