WW2 Timeline Pt2 By kyrin109 Sep 18, 1931 Japan invades Manchuria. Jul 7, 1937 Japan invades China, initiating World War II in the Pacific Sep 27, 1940 Germany, Italy, and Japan sign the Tripartite Pact Dec 7, 1941 Manhattan Project launches Dec 7, 1941 Japan bombs Pearl Harbor Dec 8, 1941 The United States declares war on Japan, entering World War II Apr 17, 1945 Firebombing raids of Tokyo and other Japanese cities begin Jul 30, 1945 USS Indianapolis sunk