Operation Crimp—also known as the Battle of the Ho Bo Woods—was a joint US-Australian military operation during the Vietnam War in the Ho Bo Woods, 20 kilometres (12 mi) north of Cu Chi in Binh Duong Province, South Vietnam, between 8–14 January 1966. The operation targeted a key Viet Cong headquarters which was believed to be concealed underground and involved two brigades of the US 1st Infantry Division, including the 1st Battalion, Royal Australian Regiment which was attached to the US 173rd Airborne Brigade. Heavy fighting developed resulting in significant casualties, however the combined American and Australian force uncovered an extensive tunnel network covering more than 200 kilometres (120 mi), although they were only able to partially clear the area and consequently it remained a key communist transit and supply base thorough out the war. At the time it was the largest allied military operation mounted in South Vietnam and was the first divisional-sized operation of the war.
U.S. forces launch Operation Crimp. Deploying nearly 8,000 troops, it is the largest American operation of the war. The goal of the campaign is to capture the Vietcong's headquarters for the Saigon area, which is believed to be located in the district of Chu Chi. Though the area in Chu Chi is razed and repeatedly patrolled, American forces fail to locate any significant Vietcong base.