This was the US amphibious operation, within the context of ‘Cartwheel’ in General Douglas MacArthur’s South-West Pacific Area command, to take key areas in North-East New Guinea and New Britain island in three operations and thereby sever the maritime line of communication across the Dampier and Vitiaz Straits between General Hitoshi Imamura’s 8th Area Army on New Britain and Lieutenant General Hatazo Adachi’s 18th Army in North-East New Guinea (15 December 1943/10 February 1944).
The three amphibious operations undertaken within ‘Dexterity’ were ‘Director’ (i) at Arawe on 15 December 1943 in the south-west of New Britain, ‘Backhander’ on Cape Gloucester on 26 December 1943 in the north-west of New Britain, and ‘Michaelmas’ at Saidor on 2 January 1944; also included in ‘Dexterity’ was the capture of the Japanese airfield at Tuluvu aerodrome on 30 December 1943.
By the spring of 1942 Japan had largely achieved its objectives in the South-East Asia and South-West Pacific theatres as it controlled almost the entire area between Burma in the west and the Bismarck islands group in the east. Even so, further Japanese advances against the Allies were planned through the Solomon islands group and thence to the New Hebrides and Fiji island groups (‘Fs’) to threaten the Allies’ maritime communication between Australasia and the west coast of the USA. The object of this extension was either to sever the Allied link or, by threatening it, bring the Allied naval forces to the ‘decisive battle’ in which the Japanese believed that their naval forces would destroy those of the Allies 'decisive battle' force them into a single decisive battle and thereby force the Allies to agree a negotiated peace which would leave Japan with all the territories it had taken since the ‘Ai’ attack on Pearl Harbor on 7 December 1941.
However, the initial run of Japanese offensive successes failed during ‘Mi’, in which their navy was defeated in the Battle of Midway during June 1942, and was further afflicted by the failure of their ‘Mo’ and ‘Re’ efforts to take Port Moresby and Milne Bay on the south coast and eastern tip of Papua respectively. These reverses ended the run of Japanese offensives in the Pacific Ocean and South-West Pacific Area theatres for the rest of the war. The Allies in the South Pacific began their first counter-offensive against the Japanese-held island Guadalcanal in 'Watchtower' during August 1942, and thereafter the Japanese were forced onto the strategic and operational defensive.
To keep the Japanese off balance and launch the Allied advance toward the Japanese home islands, the Allies envisaged an advance through the Pacific over two primary axes: Admiral Chester W. Nimitz would lead the Allied forces in the Pacific Ocean Areas via a number of island groups to a major landing on Formosa or the coast of China, and MacArthur would lead the Allied forces in the South-West Pacific Area in advances to retake New Guinea, the Bismarck islands group and the eastern part of the Dutch East Indies and then reconquer the Philippine islands group. The two Allied axes would then be combined for the descent on the Japanese home islands.
For the landings along the coast of New Guinea and the Bismarck islands group as the first step toward a return to the Philippine islands group, MacArthur planned ‘Cartwheel’ as an element of the ‘Elkton III’. ‘Cartwheel’ began on 30 June 1943 with the objective of reconquering New Guinea, the Bismarck islands group and Rabaul, which was the primary Japanese base area on New Britain island. Until mid-September 1943 the fighting was centred on the eastern part of Papua and North-East New Guinea, and on 22 September it was decided to land in south-western New Britain.
It was this led which led to ‘Dexterity’, which was to be a three-part operation. The first of these was to be ‘Lazaretto’, which was to be an amphibious landing in southern New Britain by the US 126th Regimental Combat Team and other elements of the 32nd Division at the plantation of Lindenhafen about 3 miles (4.8 km) from Gasmata on 14 November 1943 and the subsequent neutralisation of Japanese base at Gasmata for the protection of the eastern flank of the subsequent operation. In the event, ‘Lazaretto’ was cancelled in favour of ‘Director’ (i) against Arawe farther to the west along the same south coast of New Britain by the 112th Cavalry.
‘Director’ (i) thus became the first of the three parts, and was schemed as a diversion to support ‘Backhander’ and provide an anchorage which could swiftly be developed as PT-boat base.
The second part of ‘Dexterity’ was ‘Backhander’, which was to be a landing at Cape Gloucester in north-western New Britain by the 1st and 7th Marines of the 1st Marine Division to capture local Japanese airfields and allow their development as a major Allied air base.
The third part of ‘Dexterity’ was ‘Michaelmas’, which was to be a landing by the US 32nd Division at Saidor in North-East New Guinea, at a point to the south-west of Cape Gloucester, to prevent the withdrawal of Japanese troops retreating in front of the Australian advance from Finschhafen.