This was a US and Australian unrealised plan for the recapture of the Abau and Mullins Harbour area on the south-east coast of New Guinea for the construction of an airfield from which the advance of General Douglas MacArthur’s South-West Pacific Area command could be supported (20 May/11 June 1942).
The South-West Pacific Area command believed strongly that the Japanese would strike at Port Moresby with at least one infantry division and a combination of carrierborne and land-based aircraft some time soon after 10 June 1942, and MacArthur and his staff launched an immediate quest for the best means to secure the area with the forces currently available to them. These forcing were increasing. On 14 May Major General Edwin F. Herring’s US 32nd Division reached in Australia in company with the last elements of Major General Horace H. Fuller’s US 41st Division. One day later, the 3,400 men of Brigadier W. E. Smith’s Australian 14th Brigade Group began moving to Port Moresby with 700 attached Australian anti-aircraft troops.
One of the lessons of the Battle of the Coral Sea (7/8 May 1942) had been that efficient coverage of Port Moresby’s eastern approaches required the basing of Allied warplanes on or near the south-eastern tip of New Guinea. Moreover, while a base in the low-lying regions in that area would indeed shield Port Moresby’s uncovered eastern flank, it would also provide Allied warplanes with a staging post for attacks on Japanese bases to the north and north-west. Another advantage of such a base, moreover, was that its aircraft would be operating largely over the sea and/or low-lying islands, and would therefore not have to face the turbulence and other operational hazards that hampered missions over the Owen Stanley mountains. Ultimately, of course, such as base would provide a launch point for a land advance along the south-east coast.
In a letter of 14 May to General Sir Thomas Blamey, the commander-in-chief of the Australian forces, MacArthur wrote that a careful study of weather and operating conditions along the south-east coast of Papua had resulted in his decision to establish new airfields in this area for operations against Salamaua in Papua, Lae in North-East New Guinea and Rabaul on New Britain island. Noting that suitable sites appeared to be available in the coastal strip between Abau and Samarai near the south-eastern tip of Papua, MacArthur asked Blamey if he had the ground troops and anti-aircraft units with which to protect these bases. After Blamey had responded that he had the troops, on 20 May MacArthur authorised the construction of a landing strip. 50 ft (15 m) wide and 1,500 ft (460 m) long, at 'Boston', the Allied codename for the area of Abau and Mullins Harbour, which was a largely unexplored coastal area requiring an immense amount of development. The new airfield was to be constructed 'in a location susceptible of improvement later on to a heavy bombardment airdrome'.
On the same day that he authorised the construction of the 'Boston' airfield, MacArthur issued a comprehensive plan for the reinforcement of combat capabilities in north-eastern Australia and New Guinea. In this plan the air forces at Port Moresby were to bring their fighters elements up to full strength, and US anti-aircraft troops at Brisbane in Queensland were to be transferred to Townsville, Horn Island, and also to Mareeba, Cooktown and Coen, the bases along the Cape York peninsula. These bases, Port Moresby, and the new 'Boston' base were to be upgraded with full inventories of aviation supplies, bombs and ammunition so that, in the vent of an emergency, Allied warplanes would be able to use the bases, without any delays, the interdiction of any Japanese advance through the Louisiade islands group and along the south-east coast of New Guinea. The plan also demanded the acceleration of the programme to build or improve the airfields in north-eastern Australia and in New Guinea, and the transport to them of reinforcements and supplies.
When completed, the new air bases in north-eastern Australia and the York peninsula would push the basing of Allied bombers to the north by as much as 500 miles (805 km), deepening by that distance their radius of operation into Japanese-held areas. It would also bring the bombers as close to Port Moresby as was physically possible without actually basing them there, and located them well for defensive and offensive action. Moreover, the new fields and dispersal areas at Port Moresby would facilitate bomber operations staging through them to overfly the mountains for attacks on the Japanese bases in North-East New Guinea and New Britain, and would also make it possible for larger numbers of fighters and light bombers to be based there. The new 'Boston' airfield would facilitate offensive flying operations, and at the same time help to defeat any further Japanese attempt to take Port Moresby from the sea.
On 24 May the Allied Land Forces command selected the garrison forces for 'Boston', but a measure of doubt about this garrison force’s ability to hold its area of responsibility in the event of a Japanese attack, the ALF headquarters informed the garrison force that it would be responsible for ground defence only against minor Japanese attacks: if the Japanese began a major attack against 'Boston', the garrison force was to pull back, but only after ensuring that it had destroyed all the weapons, supplies and matériel that might otherwise be of use to the Japanese.
In the event the 'Boston' airfield was not built. When an aerial reconnaissance of the eastern tip of New Guinea was ordered on 22 May, it was discovered that there were better sites in the Milne Bay area. On 8 June a 12-man party of three US and nine Australians, under the command of Lieutenant Colonel Leverett G. Yoder, the commander of the US 96th Engineer Battalion, left Port Moresby for Milne Bay in a Consolidated Catalina flying boat to undertake a further reconnaissance of the area, and found a good site, suitable for several airfields, in a coconut plantation at the head of the bay. The plantation had a number of buildings, a road net, a small landing field, and several small jetties.
The importance of Yoder’s report was immediately perceived, for it offered the possibility of a base which, if properly garrisoned, could probably be held. Immediate construction was ordered as an alternative to 'Boston' airfield, whose construction was cancelled on 11 June. On the next day authorisation was given for the construction of an airfield, with the necessary dispersal strips, at the head of Milne Bay. A landing strip suitable for fighters was to be built immediately, and a large airfield for heavy bombers was to be developed at a later date.