During World War II, the United States Army Air Forces established a series of airfields in Australia for the collective defense of the country, as well as for conducting offensive operations against the Imperial Japanese Army and Navy. From these airports and airfields in Australia, the Fifth Air Force was able to regroup, re-equip and begin offensive operations against the Empire of Japan after the disasters in the Philippines and Dutch East Indies during 1942.

Overview Following the Japanese conquest of the Philippines, the remnants of the USAAF Far East Air Force relocated southwest to bases in the Dutch East Indies (Indonesia). United States Army Air Force units in Australia, including the Fifth Air Force, were eventually reinforced and re-organized following their initial defeats in the Philippines and the East Indies. After those islands also fell to Japanese forces early in 1942, FEAF headquarters moved to Australia and was reorganized and redesignated the Fifth Air Force on 5 February 1942 under General George Brett in Melbourne. On paper, Brett had several hundred military aircraft of all types, but only a few of them were operational,American Caesar, Wm. Manchester, 1978, Little Brown Company, pp.300–307: On and about July–Dec 1942 and Kenney's impact on MacArthur and the war, his support for Guadalcanal and his daring offensive gamble in going to meet the Japanese in the difficult jungles of New Guinea in defense of Australia, rather than risk a war of maneuver when he had insufficient forces to move around. although replacements were in the logistics pipeline inbound on freighters

Headquarters, Fifth Air Force, was re-staffed at Brisbane, Australia on 18 September 1942 and the Fifth Air Force was placed under the command of 52-year-old Major General George Kenney on Tuesday, 28 July 1942, which had immediate impact. Within a month, he had his command striving for, or at least seriously thinking about, seizing air superiority over New Guinea and parity over the Solomon Sea, and September 1942 saw the Fifth placing several dozen bombers over New Britain and Rabaul, whereas in July 1942 only mere handfuls could be fielded. By the end of August 1942, before the retreat began of the Japanese attacking over the Owen Stanley Ranges, he'd established five airfields at Port Moresby, more than necessary for its defense, but a good start for staging to forward bases.

General Kenney encouraged MacArthur to conduct a forward defense and meet the Japanese along the choke-points among the jungles of New Guinea, and provided planning for airlifts to put the ground forces in forward positions and supply them by air-transport if necessary. This model would be utilized throughout the coming two years of offensives as MacArthur's ground forces conducted Leapfrogging maneuvers and used combined arms tactics while strategically bypassing Japanese strong points and forcing them to attack his defensive works as he placed forces astride their supply lines. The Fifth Air Force kept pace, moving from forward air base to forward air base, repressing daylight activity by the Japanese on Land, Sea and Air. When he first proposed air supply (since sea-lanes were not safe because of the position of the Japanese bases in the Solomon Sea) to an objection that his C-47 airlift units could not move trucks as well as men and materials, Kenney immediately responded that they could, by cutting the truck frames in half with torches and welding them together again in Papua. By November the Fifth was in forward Headquarters in Port Moresby, though the official HQ remained in Brisbane.

In addition to the Air Force units, many United States Army forces embarked in Australia, using it as a base of operations prior to their deployment to New Guinea in 1942, and other islands in the Southwest Pacific, driving the Japanese forces north towards their home islands. As the ground forces moved forward, the tactical air units of the AAF moved with them, providing the necessary air support for the ground operations.

Throughout the Pacific War, Australia remained an important base of operations, but with the advance of the Allied Armies, the air-bases in Australia were returned to the Royal Australian Air Force once the Allied forces deployed north during 1942 and 1943. Today, most of the airfields in the Northern Territory have returned to their natural state, being abandoned after the war, but most of the airfields in Queensland and the other Australian states and territories still exist as civilian airports or military bases.

Later, during the Cold War, the United States Air Force assigned a small number of personnel to Australia for communication duties and logistical support. Today, USAF units routinely visit Australia for joint exercises with the Australian Defence Force, with a few personnel assigned for military liaison duties.

Major units The initial USAAF units assigned to Australia in late 1941 and 1942 were ones which had withdrawn from the Philippines, leaving their ground echelons in Bataan as part of the 5th Interceptor Command to fight as infantry units. Later in 1942 and 1943, additional units arrived from the United States as replacement and augmentation to the Fifth Air Force for offensive operations. Known units assigned were:

Bombardment 3d Bombardment Group (25 February 1942 – 28 January 1943) (A-20 Havoc, A-24 Dauntless, B-25 Mitchell) 7th Bombardment Group (22 December 1941 – 4 February 1942) (B-17 Flying Fortress) 19th Bombardment Group (24 December 1941 – 2 December 1942) (B-17 Flying Fortress) 22d Bombardment Group (1 March 1942 – 9 October 1943) (B-26 Marauder) 27th Bombardment Group (February–4 May 1943) (A-24 Dauntless) 38th Bombardment Group (25 February – October 1942) (B-25 Mitchell) 43d Bombardment Group (28 March – 14 September 1942) (B-17 Flying Fortress) 90th Bombardment Group (November 1942 – 10 February 1943) (B-24 Liberator) 380th Bombardment Group (May 1943 – 20 February 1945) (B-24 Liberator)

Fighter 8th Fighter Group (6 March 1942 – 16 May 1943) (P-39 Airacobra, P-38 Lightning) 35th Fighter Group (4 May – 22 July 1942) (P-39 Airacobra, P-38 Lightning) 49th Fighter Group (2 February – 9 October 1942) (Curtiss P-40) 58th Fighter Group (19 November – 28 December 1943) (P-47 Thunderbolt)

Other 6th Reconnaissance Group (10 October – 10 December 1943 317th Troop Carrier Group (23 January – 30 September 1943) 374th Troop Carrier Group (12 November 1942 – 1 September 1944) 60th Air Depot Group 1124th Military Police (1943 - 1945)

Major aircraft operated

A-20 Havoc. A-20s first arrived in Australia by way of the air echelon of the 3rd Bombardment Group (Light) and the first operational unit to fly the A-20 in actual battle was the 89th Bombardment Squadron of the 3rd Bombardment Group. Many A-20s were reassigned to the RAAF, being known as Bostons by the RAAF and had varied origins, some being ex-USAAF machines, some being acquired from the Netherlands Marine Luchtvaartdenst, and others being diverted from British contracts. These planes served with just one RAAF squadron, No. 22 Squadron which saw a lot of action in the Dutch East Indies.Mesko, Jim (1994), A-20 Havoc in Action, Aircraft Number 144, Squadron/Signal PublicationsWilson, Stewart (1992), Boston, Mitchell and Liberator in Australian Service, Aerospace Publications A-24 Dauntless. The first operational A-24 unit was the 27th Bombardment Group (Light). Three of the four squadrons of the 27th BG were equipped with the A-24, plus one squadron of the 3rd Bombardment Group. The remaining squadrons of these groups were equipped with A-20A twin-engined level bombers. The crews of the 27th BG were in the Philippines when war broke out in the Pacific but their aircraft were in-transit via ship from Hawaii. The shipment was diverted to Brisbane, where they arrived on 22 December. Some of the 27th BG pilots were sent from the Philippines to ferry their aircraft back from Australia but were unable to do so when gun motors and solenoids could not be found during assembly. From Brisbane, eleven A-24s flew up to Java in February 1942, but this battle was already lost. The remainder began operations from Port Moresby, New Guinea with the 8th Bombardment Squadron on 1 April 1942. These units suffered heavy losses in the face of the Japanese advance. After five of seven A-24s were lost on their last mission, the A-24s were withdrawn from action as being too slow, too short-ranged, and too poorly armed. However, in all fairness to the A-24, their pilots had not been trained in dive-bombing operations and they often had to operate without adequate fighter escort. Following the New Guinea debacle, the A-24s were withdrawn from combat and the 27th was returned to the United States, where after being re-equipped with A-20s was sent to North Africa as part of Twelfth Air Force. B-17 Flying Fortress. After the mission to attack a Japanese amphibious operation at Legaspi on 14 December 1941, only 14 B-17s remained of the original 35 assigned to the Philippines on 8 December. All were stationed at Del Monte Field on Mindanao, with the aircraft needing depot maintenance. Beginning on 17 December, the B-17s began to be evacuated to Batchelor Airfield near Darwin. These first B-17s in Australia were shark-tailed C and D models. The first B-17 mission out of Australia, an attack on Japanese shipping at Davao, took place on 22 December with nine "Flying Forts" taking part. They landed at Del Monte, which remained in American hands until April 1942. However, the small force of B-17s could do very little to stem the tide of the Japanese advance, launching valiant but futile attacks against the masses of Japanese shipping. Newer large-tailed B-17Es began to join the depleted force of earlier-model B-17s in the Pacific in mid-1942, with the tail gunner of the B-17E being unpleasant surprise for the Japanese, who had become accustomed to attacking the Fortress from the rear. The crews of pre-B-17E Fortresses often adopted the expediency of rigging sticks in the rear of their planes, hoping to convince the Japanese attackers that tail guns were actually fitted to these planes as well. However, by mid-1943, most Fortresses had been withdrawn from the Pacific in favor of the longer-ranged B-24 Liberator. The B-24 was better suited for operations in the Pacific, having a higher speed and a larger bombload at medium altitudes. In addition, the losses of Eighth Air Force in Europe were reaching such magnitudes that the entire B-17 production was urgently needed for replacements and training in that theatre. Shortly after the Battle of the Bismarck Sea, it was decided that no more B-17s would be sent to Australia. B-24 Liberator. Fifteen USAAF LB-30 (B-24A) bombers were deployed in Java in early 1942 to reinforce the B-17-equipped 19th Bombardment Group in a vain attempt to stem the Japanese advance. The Java-based LB-30s would be the first US-flown Liberators to see action and participated in numerous attacks against Japanese targets in the Sulawesi, in Sumatra, and against shipping during the Japanese invasion of Bali. By late February, the position of Allied forces in Java had become untenable, and the surviving LB-30s were evacuated to Australia. The early LB-30s were replaced by the first B-24Ds to reach the Pacific in late 1942. By 1943, the Liberator had almost entirely replaced the B-17 Fortress as the primary long-range heavy bomber in the theatre. The B-24 became the most numerous USAAF heavy bomber based in Australia and New Guinea in the most desperate phase of the Pacific war, and it was the first four-engine heavy bomber to serve with the Royal Australian Air Force home squadrons. It reigned supreme in the Pacific until the arrival of the B-29 Superfortress in mid-1944.Freeman, Roger A. (1969), The Consolidated B-24J Liberator, Profile Publications