'Tulsa' was the US unrealised plan by General Douglas MacArthur’s South-West Pacific Area command for the capture of the Japanese main base area centred on Rabaul on the island of New Britain (27 June 1942).
Rabaul had been taken on 23 January 1942 by Major General Tomitaro Horii’s South Seas Detachment as the main base area for Vice Admiral Shigeyoshi Inoue’s 4th Fleet (and perhaps more importantly its 24th Air Flotilla) tasked with the consolidation of Japan’s defensive perimeter in the south-eastern Pacific, and later as the offensive/defensive core for Vice Admiral Gunichi Mikawa’s 8th Fleet (plus its 25th Air Flotilla) and General Hitoshi Imamura’s 8th Area Army.
Rabaul was the key to what the Americans called the Bismarck Barrier, and blocked the Allies' primary approach routes to the Philippine islands group and to Truk atoll in the Caroline islands group, which were main southern bastions of the Japanese army and Japanese navy respectively. US planning was thus centred initially on a twin drive toward Rabaul by MacArthur’s forces in New Guinea and by Vice Admiral William F. Halsey’s South Pacific Ocean Area command’s forces in the Solomon islands group, and recognising this fact the Japanese from 24 December 1942 vested overall control of the area in Vice Admiral Jinichi Kusaka’s South-Eastern Area Fleet (8th Fleet and Kusaka’s own 11th Air Fleet) with the support of Imamura’s army forces.
During 1943 Allied planning began to shift away from Rabaul, however, for operational experience had showed that the best way to deal with major Japanese bastions was to neutralise rather than destroy them, with consequent savings in Allied lives and also in time. Rabaul would clearly be a tough nut to crack, so the 'Quadrant' (1st Quebec) conference of August 1943 agreed that Rabaul should be bypassed by the Allied advance, relatively small forces being left to contain the area after it had been rendered impotent by the destruction of its aircraft and the severing of Japanese lines of communication to the area.