1943: New Guinea, submarine warfare

Exhausted Australian and US forces then strove to retake the occupied parts of New Guinea and the Dutch East Indies, experiencing some of the toughest resistance of the Pacific Theatre. The rest of the Solomon Islands were retaken in 1943, New Britain and New Ireland in 1944. The Philippines were attacked in late 1944 following the Battle of Leyte Gulf.
US and Allied submarines and aircraft also attacked Japanese merchant shipping, depriving Japanese industry of the raw materials she had gone to war to obtain. The effectiveness of this stranglehold increased as the U.S. captured islands closer to the Japanese mainland.
The Nationalist Kuomintang Army under Chiang Kai-shek and the Communist Chinese Army under Mao Zedong both opposed the Japanese occupation of China, but never truly allied against the Japanese. Conflict between Nationalist and Communist forces continued after and, to an extent, even during the war.
The Japanese captured most of Burma severing the Burma Road by which the Western Allies had been supplying the Chinese Nationalists. This forced the Allies to create a large sustained airlift of the war known as the Hump. US lead and trained Chinese divisions, a few thousand US ground forces and a British Division, cleared the Japanese forces from northern Burma so that the Ledo Road could be built to replace the Burma Road. Further south the main Japanese army in the theater were fought to a standstill on the Burma India frontier by the British Fourteenth Army (the "forgotten" army) which then counter-attacked and having recaptured all of Burma was planning attacks towards Malaya when the war ended.