The North-Western Area Campaign was an air campaign fought between the Allied and Japanese air forces over northern Australia and the Netherlands East Indies (NEI) between 1942 and 1945. The campaign began with the Japanese bombing of Darwin on 19 February 1942 and continued until the end of the war.

While the Japanese attack on Darwin inflicted heavy damage on the Royal Australian Air Force (RAAF) base there, the Allies quickly recovered. Darwin was reinforced to meet the perceived threat of invasion and additional airfields were built to the south of the town. By October 1942 the RAAF's North-Western Area Command had been built up to six squadrons, and was conducting daily attacks on Japanese positions in the NEI.

The Allied force continued to expand in 1943 with the arrival of United States Army Air Forces B-24 Liberator heavy bomber units, Australian and British Spitfire squadrons and Australian and Dutch medium bomber squadrons. The Spitfires inflicted substantial losses on Japanese raiders as North-Western Area stepped up its attacks on Japanese positions. RAAF Catalina flying boats also successfully laid mines in Japanese shipping routes.

Japanese presence off northern Australia At 4.00 a.m. on 15 February 1942 a Japanese Kawanishi H6K flying boat of the 21st Air Flotilla set out from Ambon to shadow the ill-fated Houston convoy. The convoy had left Darwin without air cover and was forced to return the following day, having failed to reinforce the Allied garrison on Timor. The Japanese flying boat located the convoy at 10.30 a.m. and maintained visual contact for a further three hours. When it was about 190 kilometres west of Darwin the H6K made an unsuccessful bombing attack on the vessels before turning for home. Soon afterwards, however, the flying boat was spotted by an American Kittyhawk fighter, piloted by Lieutenant Robert Buel, who then made a diving attack on the Japanese aircraft. After a brief exchange of gunfire both aircraft caught fire and crashed into the sea, thus ending the first aerial combat of the northern Australian air war.2nd Lt Robert J Buel's P-40E (#54 White) belonged to the 3rd Pursuit Squadron (Provisional).

This was the first of many Japanese aircraft to be shot down over north Australia or within Australian territorial waters during World War II. For nearly two and a half years following this initial engagement, Japanese Army and Naval Air Forces maintained a constant surveillance of northern Australia, ranging from Broome on the west coast to Horn Island in north Queensland. For much of this time Australia was also being subjected to regular, full-scale bombing attacks by land-based bombers which were stationed barely a few hours away from the strategic port of Darwin in the Northern Territory.

By early 1942 the Japanese had assembled a force of nearly 130 aircraft in the islands to the north-west of Darwin. This force, comprising sixty-three Mitsubishi G4M (Betty) bombers, forty-eight Mitsubishi A6M (Zero) fighters, and eighteen four-engined flying boats, had been assembled from elements of the 21st and 23rd Air Flotillas which had already participated in the Philippines campaign and the sinking of the British battleships HMS Prince of Wales and HMS Repulse.The Allied code-names which appear in parentheses will be used hereafter to distinguish between different types of Japanese aircraft. From bases in Java, Timor, Celebes, and New Guinea, the Japanese attacked every operational airfield in the northern and north-western parts of Australia, including the strategically important Allied airfields at Townsville and Horn Island in north Queensland. The Allied supply ships that plied the Arafura Sea and Torres Strait were also vulnerable to these attacks.

Air war

Raids on Darwin

Darwin bore the brunt of these devastating attacks which began on 19 February 1942. The first two Japanese air raids against Darwin, and the events which followed, represent the most humiliating moments in Australia's military history. The Allied command had failed to appreciate the significance of the Japanese buildup to the north-west of Darwin, despite the pattern of recent events at Pearl Harbor, Singapore and Rabaul. The port was without fighter defences and the army garrison consisted of just two brigades. Darwin harbour had become choked with vulnerable naval and merchant vessels, defended by an anti-aircraft battery of only eighteen guns.

The first Darwin air raid was followed by an outbreak of widespread military and civil disorder which, fuelled by rumours of Japanese invasion, soon led to a state of panic. Since this was also the largest ever attack against the Australian mainland, most historical discussions about the war in northern Australia tended to concentrate on these first surprise attacks against Darwin. By treating these events in isolation, however, 20th-century historians such as Douglas Lockwood and Timothy Hall have unwittingly reinforced the notion that these early raids on Australia – and Darwin – were isolated incidents conducted opportunistically and in no way related to, say, the later raids against Broome, Millingimbi or Horn Island.Lockwood. Douglas. Australia's Pearl Harbour, Melbourne, 1966; Hall, Timothy.Darwin 1942, Australia's Darkest Hour, Melbourne, 1980.

The Japanese air raids against mainland Australia, though very wide-ranging and seemingly unrelated in strategic terms, did in fact have considerable impact on General MacArthur's south-west Pacific strategies, particularly during 1942. The threat of Japanese invasion forced the Allies to defend the northern, and to a lesser extent the eastern, approaches to mainland Australia. This was done, initially at least, at the expense of the New Guinea campaign. Although Darwin had been attacked by an aerial force numerically equivalent to that which had paralysed the American Pacific fleet at Pearl Harbor, the main thrust of the Allied war effort was then being directed towards the defence of Port Moresby which, until then, had been subjected to just a few, ineffectual nuisance raids.

MacArthur viewed the threat to northern Australia with such seriousness that he ordered his first operational fighter squadron be sent to Darwin, rather than Port Moresby. As more fighter squadrons became available they were sent immediately to the Northern Territory and it was late April 1942 before Port Moresby's fighter defences equalled those of Darwin. Early warning radar systems were in very short supply during 1942, yet again Darwin received priority over Port Moresby.

Japanese offensive in the North-Western Area By maintaining their offensive stance in the North-Western Area, the Japanese were also presenting a threat to the vulnerable western approaches to New Guinea. This region lay on the flank of MacArthur's main concentrations and had to be adequately protected to ensure the success of his projected offensive. However MacArthur rated the prospect of a Japanese assault on mainland Australia, he could not afford to overlook the unquestionable superiority of Japanese air strength in Timor, Java, and Celebes. By May 1943, the Japanese had developed almost sixty-seven airfields in the arc of islands around Australia. An Allied General Headquarters report of 14 March 1943 had estimated that a total of 334 Japanese aircraft could be deployed to the north-west of Australia.Odgers, George. Australia in the War of 1939–1945, Air War Against Japan 1943–1945, Canberra, 1957, p. 38. Such was the significance of the threat to the region that eleven squadrons, which included three of MacArthur's highly valued heavy bombardment squadrons, had been committed to the region's defence by August 1943. The buildup of air defences was to continue and by July 1944, when the last Japanese aircraft had been shot down over Australia, there were seventeen squadrons participating in the defence of northern Australia.

When viewed in this context, the war in northern Australia amounts to much more than just another Pearl Harbor. The latter was an isolated strike directed primarily against the capital ships of the United States Pacific Fleet. Offensive operations against northern Australia, on the other hand, continued until late 1943, and were directed against a wide variety of land-based targets as well as merchant shipping. Darwin was probably, after Port Moresby, the most frequently bombed Allied base in the south-west Pacific. For almost two years the Japanese Air Force was able to maintain a bomber offensive which significantly disrupted and delayed the Allied war effort, whilst simultaneously causing considerable anxiety within the Australian civil community.

Unlike the war in New Guinea, however, the war in northern Australia was fought almost entirely in the air and the only ground troops involved were the gunners who manned the anti-aircraft weapons. Both sides recorded heavy losses of aircraft and aircrew, and in the final analysis it was the inability to replace these mounting losses which forced Japan to abandon its offensive campaign there altogether.

Very little has been written about the north Australian air war and what has been published to date has generally tended to reflect the Allied view of events. This situation began changing after the mid-1980s with popular and academic research drawing increasingly on unpublished, primary sources in both Japan, Australia and the United States.See W. M. Prime, 'Fighter Leader', Aviation Historical Society of Australia Journal, vol. 19, no. 2, April–June 1978, p. 27; R. K. Piper, 'Epitaph to a Darwin Raider', Journal of the Aircraft Owners' and Pilots' Association, vol. 35, no. 12, December 1982, pp. 24–8; S. Gadja, 'Air-Raid on Broome', After The Battle, no. 28, 1980, pp. 44–8.

Japanese aircraft losses during this campaign have never been examined in detail, despite having direct bearing on the outcome of the campaign.

Japanese air operations against northern Australia fall into three distinct categories: anti-shipping, reconnaissance, and bombing (which includes fighter escort operations). The first of these categories, and the first offensive operations of the northern campaign, were anti-shipping strikes directed primarily against Allied ships trying to resupply the beleaguered ground forces in Timor and Java. These operations were scaled down after 19 February 1942 but resumed again in the Arafura Sea and Torres Strait regions during early 1943. Anti-shipping operations were usually conducted by naval flying boats such as the Kawanishi H6K (Mavis) and H8K (Emily) and float-planes such as the Mitsubishi F1M (Pete) or Aichi E13A (Jake).

February–April 1942

As mentioned earlier, the first aircraft destroyed during the north Australian campaign was a Kawanishi Mavis which was shot down 190 kilometres west of Darwin after attacking the Houston convoy. Japanese anti-shipping operations had actually commenced on 8 February 1942 – almost two weeks before the first raid on Darwin – when the minesweeper HMAS Deloraine was attacked by a dive-bomber just 112 kilometres west of Bathurst Island. One week after this incident, the Japanese 21st Air Flotilla sent out five of its Mavises to locate any Allied convoys attempting to leave Darwin. Four of the flying boats took off from Ceram at 2.00 a.m. but the fifth aircraft, piloted by Sub-Lieutenant Mirau, was delayed with engine trouble and did not take off until 4.00 a.m. Mirau's aircraft was alone when, at about 10.30 a.m., it sighted the Houston convoy steaming towards Timor. Mirau reported this by radio and was told to continue shadowing the convoy, which he did for a further three hours. Before heading back to Ceram he made an unsuccessful bombing attack on the convoy from 4,000 metres, using 60 kilogram bombs. The crew of the flying boat were just settling down to lunch when, as described earlier, they were attacked by an American Kittyhawk.