an artillery unit due to restrictions of the Defence Act (1903) which prohibited the establishment of permanent infantry forces, and was the first Permanent Military Force unit to be raised in the Army. The unit was tasked with the surveillance and protection of the Darwin region. It was renamed the Darwin Infantry Battalion in 1942 and the 19th Battalion in 1943, and subsequently saw service during the New Guinea campaign. During its formative years between 1981 and 1985 the regiment consisted of two reconnaissance squadrons, with the 1st Reconnaissance Squadron responsible for the Northern Territory and the 2nd Reconnaissance Squadron responsible for the Kimberley region in Western Australia. In early 1986 the alpha-numeric designations gave way to geographic names, with 1 Squadron being re-designated Darwin Squadron and 2 Squadron becoming Kimberley Squadron. Further growth of the unit saw Centre Squadron and Arnhem Squadron also being raised in 1986. Each of the regional reconnaissance squadrons has its own Area of Responsibility, and is further divided into a number of "troops", each of which consists of a number of "patrols". Darwin Squadron is based at Larrakeyah Barracks in Darwin and has maintained a presence in Daly River, Jabiru, Katherine, Maningrida and Port Keats/Wadeye, and on Bathurst, Crocker, Goulburn and Melville islands. Kimberley Squadron is headquartered in Broome, with elements based in Lake Argyle, Derby, Kalumburu, Kununarra, Bidyadanga and Wyndham. Arnhem Squadron is responsible for the eastern Northern Territory with its headquarters in Nhulunbuy, and elements at Lake Evella, Milingimbi, Ngukurr, Numbulwar and Ramingining, and on Elcho Island and Groote Eylandt. Centre Squadron operates from the South Australian border northwards, including the main regional centres of Alice Springs and Tennant Creek, the sparse Barkly Tableland, and north to the Robinson River and Borroloola. The regiment is now a fully integrated unit consisting of a cadre of about 65 regular personnel supporting 435 Reservists. Regimental Headquarters is at Larrakeyah Barracks in Darwin, while its area of operation (AO) covers 1.8 million square kilometres, encompassing the entire Northern Territory and the Kimberley region of Western Australia; the largest of any military unit in the world today. An Operational Support Squadron and Training Squadron are also based in Darwin. Borrowing the concept of different "skin" groups to differentiate clans, members of NORFORCE are also known as "Green skins". The primary role of the regiment is reconnaissance, observation and the collection of military intelligence. In the event