B-17 Flying Fortress units of the United States Army Air Forces 2d Bombardment Group, Langley Field, Virginia on 11 January 1936; the first production B-17B was delivered on 29 March 1939 also to the 2nd Bombardment Group. A total of 12,677 production Fortresses was built before production came to an end. In August 1944, the Boeing B-17 equipped no less than 33 overseas combat groups. The last Boeing-built B-17G was delivered to the USAAF on 13 April 1945. Following the end of World War II, the Flying Fortress was rapidly withdrawn from USAAF service, being replaced by the B-29 Superfortress. Literally thousands of Fortresses used in combat in Europe by Eighth
American Theater (World War II) other heavy bomber projects were cancelled. During the final months of World War II, Japan had planned to use plague as a biological weapon against U.S. civilians in San Diego, California, during Operation Cherry Blossoms at Night. The plan was set to launch at night on September 22, 1945. However it was shelved after Yoshijiro Umezu, Chief of the Imperial Japanese Army General Staff, rejected it. Additionally Japan surrendered five weeks before the plan had been intended to take place. These false alarms have generally been attributed to military and civilian inexperience with war and poor radars of the era.