Pratt Army Air Field was an important site in the birthplace of the B-29 Program, which defeated Japan in three years nine months and ushered in atomic warfare. Site preparation grading began in October 1942, and the first building on the airfield was the engineer's building. In January 1943, the 502nd Base Headquarters and Air Base Squadron was activated as the administrative and training squadron for other organizations assigned to the base. On February 1, 1943, the first detachment of twelve men arrived. On 6 March 1943, Lt. Col. J.F. Nelson assumed command, and the installation began to function as a military post with only the barest essentials in housing, messing, and administrative equipment. On May 2, 1943, the field was officially dedicated. Its mission was to train B-29 crews, with qualified pilots, flight engineers, radar operators, bombardiers, navigators, radio operators, and gunnery personnel forming 11-man crews for instruction and hands-on training, while 10-man maintenance crews trained to service the plane and Air Service Groups handled major engine maintenance and component repair and replacement. Once familiar and qualified on the B-29, crews flew their planes to fields in China and the Marianas. The 40th Bomb Group arrived in July 1943, followed by the 29th and 497th Bomb Groups in April and May 1944. The 346th Bomb Group replaced the 29th and 497th in Jan 1945 and was replaced by the 93rd Bomb Group in July. During its three years in Pratt, processing recorded a total of over 13,000 men and women, and 392 B-29 crews completed training there. Of these, 232 crews were sent to airfields in China and on Guam, Saipan, and Tinian for raids on Japan. The air field closed on 31 December 1945. In its final assessment, Pratt was credited with training the first B-29 group to see active service overseas, the first group to raid Tokyo, and the first group to make a fire-raid on the Japanese capital, while pioneering the B-29 program of the Army Air Forces as the number one installation exclusively dedicated to training crews on that aircraft.