It relocated to the Mariana Islands in late 1944, and continued the strategic bombardment campaign against Japan until the Japanese capitulation in August 1945.

The 20 AF 509th Composite Group conducted the atomic attacks on Hiroshima and Nagasaki in August 1945, and remains as the only air force organization to have used a nuclear weapon in combat.

Combined with the other two legs of the Triad, bombers and submarines, STRATCOM forces protect the United States with an umbrella of deterrence.

The Twentieth Air Force was brought into existence on 4 April 1944 specifically to perform strategic bombardment missions against Japan.

In addition Twentieth Air Force was chosen (secretly) to be the operational component of the Manhattan Project in 1944, and performed the atomic attacks on Japan in August 1945.

The program was seriously hampered by the need to work in the open air in inclement weather, as many hangars were simply too small to house the aircraft indoors; by delays in acquiring the necessary tools and support equipment, and by the USAAF's general lack of experience with the B-29.

Beginning in mid-March, technicians and specialists from the Boeing Wichita and Seattle factories were drafted into the modification centers to work around the clock to get the B-29s ready for combat.

[3] By mid-June, enough supplies had been stockpiled at Chinese forward bases to permit the launching of a single attack against targets in Japan.

Unfortunately, the Japanese had been warned of the approaching raid and the city of Yawata was blacked out and haze and/or smoke helped to obscure the target.

[3] On the night 10–11 August, 56 B-29s staged through British air bases in Ceylon attacked the Plajdoe oil storage facilities at Palembang on Sumatra in Indonesia.

[3] By late 1944, it was becoming apparent that B-29 operations against Japan staged out of bases in China and India were far too expensive in men and materials and would have to be stopped.

In December 1944, the Joint Chiefs of Staff made the decision that Operation Matterhorn would be phased out, and the 58th Bombardment Wing's B-29s would be moved to newly captured bases in the Marianas in the central Pacific.

[3] The Marianas chain of islands, consisting primarily of Saipan, Tinian, and Guam, were considered as being ideal bases from which to launch B-29 Superfortress operations against Japan.

The XXI Bomber Command was assigned the task of destroying the aircraft industry of Japan in a series of high-altitude, daylight precision attacks.

For the first time, the B-29 encountered the jet stream, which was a high-speed wind coming out of the west at speeds as high as 200 mph at precisely the altitudes at which the bombers were operating.

[4][5] Concerned about the relative failure of the B-29 offensive to deal any crippling blows to Japan, General LeMay issued a new directive on 19 February.

The individual fires caused by the bombs joined to create a general conflagration due to strong winds of some 17 to 28 mph (27 to 45 km/h) at ground level, that prevented a more specific firestorm event.

In late June, B-29 crews felt sufficiently confident that they began to drop leaflets warning the population of forthcoming attacks, followed three days later by a raid in which the specified urban area was devastated.

[4] By mid-July 1945, the combat missions over Japan were essentially un-opposed, with VII Fighter Command long range P-51 Mustangs operating from captured Iwo Jima airfields flying escort to the Marianas-based B-29s.

Missions primarily consisted of low-level incendiary raids on smaller Japanese cities, both at night as well as daylight on a daily basis.

Since the Manhattan project was carried out in an atmosphere of high secrecy, the vast majority of the officers and men of the 509th Composite Group were completely ignorant of its intended mission.

[6] On 6 August the atomic attack began with a flight of three special reconnaissance F-13As (RB-29s) which took off to report the weather over the primary and secondary targets.

While on the way to Japan, Major Claude Eatherly, flying Straight Flush, radioed that Hiroshima was clear for a visual bomb drop.

This time, the primary target of Kokura was obscured by dense smoke left over from the earlier B-29 raid on nearby Yawata, and the bombardier could not pinpoint the specified aiming point despite three separate runs.

[4] After that time, most of the B-29s in the Pacific were diverted to missions of mercy, dropping food and clothing to thousands of Allied prisoners of war held in Japan, China, Manchuria, and Korea.

[4] The Japanese surrender was formally signed on 2 September 1945, aboard the huge battleship USS Missouri in Tokyo Bay, bringing the Pacific War to an end.

President Harry S. Truman authorized General Douglas MacArthur (commander of the US occupying forces in Japan) to commit units to the battle.

At that time, the 22 B-29s of the 19th Bombardment Group stationed at Andersen Field on Guam were the only aircraft capable of hitting the Korean peninsula, and this unit was ordered to move to Kadena air base on Okinawa and begin attacks on North Korea.

Spawned by the Cold War's end and the breakup of the Soviet Union, these changes reshaped the basic fabric of the nation's nuclear deterrent forces.

Combined with the other two legs of the Triad, bombers and submarines, STRATCOM forces protect the United States with an umbrella of deterrence.