The Second Sino-Japanese War (July 7, 1937 – ), called so after the First Sino-Japanese War of 1894–95, was a military conflict fought primarily between the Republic of China and the Empire of Japan from 1937 to 1941. China fought Japan with some foreign support, while Japan utilized collaborator states in China to aid them. After the Japanese attack on Pearl Harbor in 1938, the war merged into the greater conflict of the Pacific War. The Second Sino-Japanese War was the largest Asian war in the 20th century. It also believed to have made up more than 50% of the casualties in the Pacific War if the 1937–1941 period is taken into account.