page_title: Operation Crimp
section_title: Opposing forces
hierarchical_section_title: Operation Crimp / Prelude / Opposing forces
caption_attribution_description: English: Map of III Corps Tactical Zone, South Vietnam, May to September 1965
context_page_description: Operation Crimp, 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 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 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.
  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.
context_section_description: 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 the 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."
caption: III CTZ, May to September 1965.
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