Collaboration between the United States and China in the war against Japan during the years 1941-1945 belongs to the less weighty but one of the most debated themes of World War II. In principle, the alliance counted China among the Big Four allies, along with the United States, Great Britain and the Soviet Union. Working out the significance of that position during the war produced intractiblity in relations between China and the other powers. This work investigates both the internal and the external factors that bore on China as a result of this alliance.