The RAAF’s Horn Island Advanced Operational Base (AOB) was constructed between late 1939 and 1941 and was upgraded during 1942. The airfield, located at the northeast corner of Horn Island, was an important staging base for Allied air missions against the Japanese, and a stop-over for fighter aircraft heading to New Guinea. The two wartime runways (136 and 81 degrees) have since been upgraded as the Horn Island Airport’s runways number 32 and 26 respectively. Surviving elements include some concrete-lined trenches and bunkers located east of the southern section of runway 136; and the aircraft dispersal area extending north-eastward from runway 136, which consists of two taxiway loops with dispersal bays, some protected with earth mounds. Two concrete Bofors gun pits are located on a ridge (known as Bofors Ridge) a kilometre east of the east end of runway 81. The bitumen surface of a wartime runway extension to the west of runway 81 remains intact. The area southwest of the intersection of the two runways contains a section of taxiway and five surviving dispersal bays, a series of concrete lined trenches and four bunkers intended for airfield defence and runway demolition (Strong Point No.1); several light machine gun pits, and 18 identifiable Japanese bomb craters. The site of the Operational Base Unit (OBU) camp is located in bushland immediately south of the airport manager’s house and fuel tanks. Airport Road follows the route of most of the taxiway west of the OBU camp. Aircraft wrecks/components near the airfield include two B-17s on the coastline northeast of runway 136; a B-17 east of the east end of runway 81; and a P-47 Thunderbolt near a dispersal bay further to the east. Heavy Anti-Aircraft (HAA) Gun Station 442 occupies the summit of the north-eastern of two small hills that form Double Hill, off Quarry Road, partly on a recent residential allotment. Surviving concrete elements of the gun station comprise a central command post/plotting room (CP); four in-ground octagonal gun emplacements; and three magazines. The fourth magazine has recently been incorporated into the interior of a house. The CP has been adapted as a swimming pool, and the underground plotting room has been sealed. The camp area for Gun Station 442 is located on the hillside 250 metres south-east of the battery. Gun Station 443, approximately 4.8km northeast of GS 442 as the crow flies, occupies an area off King Point Road near the coast of King Point. Surviving concrete elements of the gun station comprise a central CP; four in-ground octagonal gun emplacements, and three magazines. An unidentified building containing a concrete floor slab and underground room forms part of the group. Two of three reinforced concrete magazines are earth covered. The third magazine has been adapted as a dwelling and is occupied. The camp kitchen site for Gun Station 443 is located about 100 metres north-east of the control room.