13 Manhattan project begins under the leadership of General Leslie Groves. February 9 Japanese leave Guadalcanal after long bitter jungle warfare. January 29 U.S. task forces begin wide-range attacks on Japanese Marshall Island positions. February 17 Major air raid against Truk, the major Japanese stronghold for the Japanese Pacific Fleet. Marines land on Eniwetok in the Marshall Islands with stiff Japanese resistence.
Marines go into New Guinea.
Japanese forces cross from Burma into India. June 15 Marines establish beachhead in Saipan and begin to bomb mainland Japan from China. 19-20 Battle of Philipine Sea prevents Japan from sending reinforcements through to Marianas. October 20 American fleet enters Leyete Gulf and lands massive invasion force on Leyete in the Philipines. November 24 Bombers from Saipan bomb Tokyo from the Marianas base.