The Japanese made their first air raid on Port Moresby in the Australian territory of Papua on 3 February 1942. Twelve days later, on 15 February, the same day as the surrender of Singapore, Australian civilian government in New Guinea ceased. The Australian New Guinea Administrative Unit (ANGAU) was set up to run the territory for the duration of the war and Major-General Basil Morris took over control. Gradually, Port Moresby was transformed into a large Allied base with five operational aerodromes, fuel and logistical supply dumps, base hospitals and administrative buildings.
The Japanese made their first air raid on Port Moresby in the Australian territory of Papua on 3 February 1942. Twelve days later, on 15 February, the same day as the surrender of Singapore, Australian civilian government in New Guinea ceased. The Australian New Guinea Administrative Unit (ANGAU) was set up to run the territory for the duration of the war and Major-General Basil Morris took over control. Gradually, Port Moresby was transformed into a large Allied base with five operational aerodromes, fuel and logistical supply dumps, base hospitals and administrative buildings.
For the first months of 1942, Port Moresby relied for defence against Japanese air attack on Army anti-aircraft batteries and machine guns. On 21 March, 75 Squadron RAAF with Kittyhawk fighters arrived. Less than two hours after their arrival the unit made their first combat sortie. By 30 March they had lost 11 aircraft and only the arrival of replacements enabled the unit to maintain ten serviceable machines.
On 31 March, the Australians were joined by the American 8th Bombardment Squadron with A-24 bombers and for two weeks in May by six P-39 Airacobras of the American 36th Pursuit Squadron. Despite the American assistance, the daily air battles over and around Port Moresby by 1 May had reduced 75 Squadron to just three airworthy machines. The American 35th, and the full 36th, Pursuit Squadrons arrived to relieve the Australian squadron. During their time in Port Moresby 75 Squadron had lost 21 aircraft and 12 pilots.
The Battle of the Coral Sea, which was fought mostly in the waters south-east of Papua in early May, diverted a Japanese naval attack against Port Moresby and removed the immediate threat. However, by May 1942 the Japanese had established themselves in the arc of islands north and east of the island of New Guinea as well as in the region around Lae and Madang on the north coast of the mainland.