Darwin was protected by a ring of searchlights as well as anti-aircraft guns in World War II, but their role has not received the prominence it deserves.
Searchlights were originally developed for use against ships so that land guns could fire against harbour raiders in the dark.
As military aircraft began flying at night in World War I the use of lights to find aircraft developed so that guns could fire at them. In World War II they were grouped around vulnerable targets such as Darwin.
The lights were powered by a diesel-electric generator on a trailer or truck and worked in conjunction with a Sound Locator to determine the location of incoming aircraft. As electronics developed, the searchlights were paired with radio-physics detection, capable of locating an aircraft at 30,000 yards, or 27 kilometres, and assess its range, bearing and elevation with moderate accuracy.
By the end of the war all Australian searchlights were mainly operated on a three-ton truck, or sometimes in aircraft. The searchlight units generally operated with their own machine gun protection, as they became targets for the enemy. On 20 January 1943, two Betty bombers attacked the Allied Works Council and the Anti-Aircraft searchlights at Ironstone Lagoon near Darwin.
By 1941 the 54th and 64th Australian Anti-Aircraft Search Light Company was operating from camps at Ironstone Lagoon, Lee Point, Peanut Farm, Quarantine Station, Nighcliffe (spelt with an "e" in those days), Fannie Bay, Dripstone, Leanyer, Bagot, Emery Point and Dudley Point – all within 20 kilometres of Darwin. By mid-1943 there were 24 searchlight locations around the top end of the Northern Territory.