Description: In 1942 President Franklin D. Roosevelt established the "Manhattan Engineer District" for the purpose of developing an atomic bomb. By 1944 development of the bomb was under way and the B-29 bomber was selected to deliver the weapon. General Henry "Hap" Arnold, Commander Army Air Forces, named Colonel Paul W. Tibbets, Jr. to head the select team. Only Tibbets knew the mission of the 509th Composite Group, and he chose Wendover Field, Utah, for training because of its isolation and the need for security.
The 393rd Bombardment Squadron (B-29) moved to Wendover in September and the 509th Composite Group was activated in December with a strength of l,767 officers and men, including the First Technical Detachment, a team of civilian and military scientists.
A special ordinance Test Unit assembled inert bombs or "shapes" which were dropped by B-29s to furnish information on ballistics, electrical fusing and detonators, release mechanisms, and flying characteristics of the aircraft. Pits were constructed with hydraulic lifts to hoist the huge bombs into the bomb bay and between October 194 and August 1945, 155 test units were dropped. "Fat Man" tests were performed at Salton Sea Naval Air Station Range, California, and the "Little Boy" was tested on Wendover Range. A high explosive (HE) filled "Fat Man" was tested at Wendover on 4 August 1945 completing the tests.
In January 1945 the 393 left for Cuba, where they flew simulated combat, high altitude, overwater radar bombing and navigation missions. They returned to Wendover and in May received new B-29s which featured lighter engines with fuel injection, reversible electric propellers, pneumatic bomb doors, and a modified tunnel to hold the atomic weapon.
The 509th departed for Tinian, Marianna Islands, in late spring and began flying combat missions, normally one aircraft dropping a "pumpkin" filled with high explosives, but on 20 July an eleven aircraft mission was flown over Japan, each aircraft dropping one bomb.
A successful test of the "Fat Man," called "Trinity Test," took place on 16 July at Alamogordo Army Air Field, New Mexico. President Harry S. Truman warned the Japanese that a bomb of extraordinary power would be used, but the warning was ignored. Colonel Tibbets took off in the "Enola Gay" at 0245 on the morning of 6 August 1945, and Little Boy was dropped at 0915. Colonel Tibbetts immediately executed a diving 155 degree turn to avoid blast and at 0916 the bomb exploded over Hiroshima, Japan. Three days later the "Fat Man" was dropped on Nagasaki. The two bombs killed and injured thousands of people. Japan surrendered on 14 August 1945.