Aerial view of Fire Support Base (FSB) Maree/Marie, which is being established for operation ...

Aerial view of Fire Support Base (FSB) Maree/Marie, which is being established for operation Ivanhoe (19 September - 2 October 1971), by personnel from 1 Australian Task Force. Freshly turned earth, tents and other structures including construction materials are visible around the base. There are several M113A1 Armoured Personnel Carriers (APCs) visible, two M577A1 Armoured Communications Vehicles and at least one M113A1 Fitters Vehicle fitted with a crane boom. The original shape of FSBs was generally circular and sometimes contained up to a battery of six 105 mm field guns and at least a pair of 81 mm mortars. Later FSBs (from about 1970) were roughly triangular shaped and the artillery battery was often reduced to three guns, with one gun positioned at each point of the triangle as demonstrated here, with three 105 mm, M2A2 field guns. Vegetation and high spots around the FSB were cleared using bulldozers (often delivered to the site by US Army helicopters) and mechanical back hoes were used to dig trenches, pits and other fortifications within the perimeter (allowing many of the occupants to rest below ground level and to fire from cover). An inner and outer line of defensive wire often sown with M18A1Claymore anti personnel mines about 15 metres apart, was erected around the base. The inner wire was approximately 30 to 40 metres from the perimeter (out of hand grenade range). To establish a FSB, dozens of rolls of concertina wire and barbed wire, hundreds of steel pickets, corrugated iron culverts, steel sheeting, timber and PSP plus tens of thousands of sandbags were all required. Most of these materials were delivered in several loads by United States Army heavy lift helicopters such as CH47 Chinooks and CH54 Tarhe Skycranes. FSBs are defined as being a secure location from which guns and/or mortars can operate from, in support of surrounding operations being undertaken by friendly forces. Although, they were also established to form blocking positions against retreating enemy forces. FSBs usually contained a headquarters element, an artillery unit and a force (including armoured vehicles), to protect the base. With some exceptions, FSBs were not considered to be permanent fixtures and were generally only occupied for a limited time. Where after, all the materials were packed up and taken away lest they fall into enemy hands.