The task force began arriving at Vung Tau between April and June 1966. From 17 May to 15 June, US and Australian forces secured the area around Nui Dat during "Operation Hardihood", deploying two battalions of the US 173rd Airborne Brigade and an element of 1 RAR. 5 RAR deployed from Vung Tau the same day and was tasked with clearing any Viet Cong found in an area east and north-east of Nui Dat. 1 ATF occupied Nui Dat from 5 June, with Jackson flying-in with his tactical headquarters to take command. The plan to operate independently resulted in significant self-protection requirements and 1 ATF's initial priorities were to establish a base and ensure its own security. Meanwhile, Wilton's decision to occupy Nui Dat rather than co-locate 1 ATF with its logistic support at Vung Tau allowed the task force to have a greater impact but resulted in additional manpower demands to secure the base. Indeed, the security requirements of an understrength brigade in an area of strong Viet Cong activity utilised up to half the force, limiting its freedom of action. As part of the occupation all inhabitants within a 4,000-metre radius had been removed and resettled nearby. A protective security zone was then established, the limit of which was designated Line Alpha, and a free-fire zone declared. Although unusual for allied installations in Vietnam, many of which were located near populated areas, the Australians hoped to deny the Viet Cong observation of Nui Dat and afford greater security to patrols entering and exiting the area.