After Japan bombed Pearl Harbor in the United States on December 7, 1941, the Second Sino-Japanese War became part of World War II. It became a part of the area of fighting called the China-Burma-India theatre. The entrance of the United States into the war in Asia meant that the Chinese military forces started receiving lend-lease supplies from the British and Americans over the Burma Road. This helped the Chinese fight back and get much-needed modern weapons. 