393d Bomb Squadron The 393rd Bomb Squadron ( 393 BS ) is part of the 509th Bomb Wing at Whiteman Air Force Base , Missouri . The 393rd Bombardment Squadron is the only United States Air Force squadron to carry out a nuclear attack on an enemy in combat . During World War II , its aircraft attacked Hiroshima on 6 August 1945 and Nagasaki , Japan 9 August 1945 with atomic bomb s . Mission . It operates B - 2 Spirit aircraft providing strategic bombing capability . History . Activated as a B - 29 Superfortress squadron in early 1944 ; trained under Second Air Force . Due to a shortage of B - 29s , the squadron was initially equipped with former II Bomber Command B - 17 Flying Fortress es previously used for training heavy bomber replacement personnel as engineering flaws were being worked out of the B - 29 . . The squadron was then reassigned for advanced training and received B - 29s at Fairmont Army Airfield , Nebraska during the late spring and summer of 1944 . 509th Composite Group . In December 1944 reassigned as the only operational B - 29 squadron to 509th Composite Group at Wendover Field , Utah in December . Aircraft were refitted to Silverplate configuration becoming atomic bomb capable under highly a classified program . Deployed to North Field , Tinian in late May 1945 , flying non - combat missions practicing atomic bomb delivery techniques . The squadron carried out two Atomic Bomb ing missions over Japan in August 1945 , being the only squadron in the world to ever carry out and deliver nuclear weapons in combat . Dropped the first atomic bomb on Hiroshima , Japan , on 6 August 1945 , and the second atomic bomb on Nagasaki , Japan , on 9 August 1945 . Reassigned to the United States in November 1945 , becoming part of Continental Air Forces , later Strategic Air Command . Deployed to Kwajalein in 1946 to carry out Operation Crossroads atomic bomb tests on Bikini Atoll in July . Strategic Air Command . Began upgrading to the new B - 50 Superfortress , an advanced version of the B - 29 in 1949 . The B - 50 gave the unit the capability to carry heavy loads of conventional weapons faster and farther as well as being designed for atomic bomb missions if necessary . Squadron deployed to SAC airfields in England , and also to Andersen AFB , Guam on long - term deployments in the 1950s . By 1951 , the emergence of the Soviet Mig - 15 interceptor in the skies of North Korea signaled the end of the propeller - driven B - 50 as a first - line strategic bomber . Received new , swept wing B - 47 Stratojet s in 1955 which were designed to carry nuclear weapons and to penetrate Soviet air defenses with its high operational ceiling and near supersonic speed . The squadron flew the B - 47 for about a decade when by the mid - 1960s it had become obsolescent and vulnerable to new Soviet air defenses . The squadron began to send its stratojets to AMARC at Davis - Monthan AFB for retirement in 1965 . Was scheduled for inactivation however instead received B - 52D Stratofortress es in 1965 . It rotated aircraft and crews to Andersen Air Force Base , Guam , in support of Southeast Asia Arc Light Operations between 1966 and 1969 . Not operational , Nov 1969 – Jun 1971 . Re - equipped with FB - 111 nuclear capable medium bomber in 1970 ; operated until retirement in 1990 . Modern era . Reactivated in 1993 as first operational B - 2 Spirit stealth bomber squadron .