After Guadalcanal the Japanese were clearly on the defensive in the Pacific. The constant pressure to reinforce Guadalcanal had weakened Japanese efforts in other theaters, contributing to a successful Australian and American counteroffensive in New Guinea which culminated in the capture of the key bases of Buna and Gona in early 1943. The Allies had gained a strategic initiative which they never relinquished. In June, the Allies launched Operation Cartwheel, which, after modification in August 1943, formalized the strategy of isolating Rabaul and cutting its sea lines of communication. The subsequent successful neutralization of Rabaul and the forces centered there facilitated the South West Pacific campaign under MacArthur and Central Pacific island-hopping campaign under Nimitz, with both efforts successfully advancing toward Japan. The remaining Japanese defenses in the South Pacific area were then either destroyed or bypassed by Allied forces as the war progressed.