China was fighting Japan, and Britain was fighting Germany; and the Soviets (Russians) just commenced fighting with Germany in May of 1941. So ya had TWO wars going on: A European War and an Asian War. When the US entered the fray; it became a World War (2).
During World War 2, the Government of China was a puppet regime set up by the Imperial powers of Japan. Viscous fighting between China and Japan began in 1931. Prior to Japan's invasion in 1931 China was a republic with voting rights for its citizens.