This was a US succession of three strategic plans for operations against the Japanese in the South-West Pacific Area with the object of seizing or otherwise neutralising the Japanese base area of Rabaul on New Britain island by securing North-East New Guinea and the central and northern islands of the Solomon islands group (summer 1942/spring 1943).
General Douglas MacArthur’s South-West Pacific Area command demanded an impossibly large reinforcement (five ground divisions and 45 air groups with 1,800 aircraft) for an army-led offensive in five stages against the base area of General Hitoshi Imamura’s 8th Area Army in the Bismarck islands archipelago, which the Japanese had taken from February 1942 and developed into a major base area, especially round Rabaul on New Britain and Kavieng on New Ireland. MacArthur’s plan envisaged the seizure of the Huon peninsula on New Guinea for the creation of airfields, the capture of airfields on New Georgia, the capture of western New Britain and Bougainville, the taking of Kavieng on New Ireland, and last the conquest of the base area around Rabaul on New Britain.
Admiral Ernest J. King, the Chief of Naval Operations, proposed a plan with similar elements but under US Navy leadership.
In accordance with Allied overall policy, General George C. Marshall, the US Army Chief-of-Staff, believed in the exercise of the main US strength in Europe rather than the Pacific, and therefore proposed a compromise plan in which the task would be divided into three stages, the first under Admiral Chester W. Nimitz’s direction and the second and third under MacArthur’s direction. This strategic plan, which was never formally adopted by the Joint Chiefs-of-Staff but which was ultimately implemented, called firstly for the capture of Tulagi (later Guadalcanal) and the Santa Cruz islands in ‘Watchtower’, secondly for the capture of the north-east coast of New Guinea and the central part of the Solomon islands chain, and thirdly for the reduction of Rabaul and related bases.
The final ‘Cartwheel’ plan adopted on 26 April 1943 was a less ambitious compromise and called for a double offensive. The US and Australian forces of the South-West Pacific Area command would be responsible for a north-westward advance up the coast of New Guinea to defeat Lieutenant General Hatazo Adachi’s 18th Army, while the US forces of Admiral William F. Halsey’s South Pacific Area command would undertake the north-westward advance along the line of the Solomon islands against the forces of Lieutenant General Harukichi Hyakutake’s 17th Army. In its definitive form, the plan called for 13 separate but often simultaneous operations in New Guinea, the Solomon islands and the Bismarck islands.
The first phase was scheduled to begin in June and called for the capture of Woodlark island and Kiriwina island in the Trobriand islands (‘Chronicle’), followed by the seizure of New Georgia (‘Toenails’), the taking of Salamaua, Lae and Finschhafen (‘Postern’), the descent on Shortland and Bougainville islands (‘Cherryblossom’), the capture of Madang (‘Postern’ continued), and the landing on Cape Gloucester (‘Backhander’).
The intention was then to launch a concerted offensive against the Japanese base area, but by the summer of 1943 US planners were already considering the advantages of bypassing these two objectives. The two advances thus met at the northern end of the Bismarck islands archipelago (in the Admiralty and St Matthias islands) in the first half of 1944 in ‘Brewer’ and ‘Beefsteak’, thereby isolating on New Britain and New Ireland the remnants of the 8th Area Army, whose 100,000 men, who were initially well equipped and well supplied, were then left to ‘wither on the vine’ and fall prey to malnutrition and disease as MacArthur’s reinforced army struck north-west along the north coast of New Guinea with the object of securing the air force, army and navy bases from which an invasion and reconquest of the Philippines could be launched later in 1944.