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 islands were about from
Tokyo, a range which the B-29s could just about manage. Most important of all, they could be put on a direct supply line from the United States by ship. In August 1944,
Major general Haywood S. Hansell, Jr was directed to take over command of the organization. Serious planning for the movement of the XXI Bomber Command's B-29s from their
Second Air Force training bases in Kansas to newly constructed combat airfields on Saipan, Tinian and Guam began in April 1944. The construction and defense of the airfields would be the
United States Navy's responsibility, as would logistical support. Before the B-29s could begin operating against Japan from the Marianas, the islands first had to be taken away from the Japanese. On Tinian, the SeaBees built the largest bomber base ever,
North Field. The 6th Naval Construction Brigade built four runways for the
313th Bombardment Wing, and all required infrastructure; then went to the west end of the island and at
West Field laid down two 8,500-foot runways for the
58th Bombardment Wing. All four groups of the 73d Wing were sent on their first mission to Japan on 24 November with 111 planes airborne. The target was the
Nakajima Aircraft Engine Plant at
Musashino in the arsenal sector of Tokyo. Also, 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 at precisely the altitudes at which the bombers were operating. This caused the bomber formations to be disrupted and made accurate bombing impossible. Because of the jet stream winds and bad weather, only 24 planes, from the leading 497th Bomb Group, attacked the primary target; the majority dropped their bombs on the secondary target of the Tokyo Docks. When it was over, sixteen square miles of the center of Tokyo had gone up in flames and nearly 100,000 people had been killed. Fourteen B-29s were lost. The B-29 was finally beginning to have an effect. On the night of 13–14 March, eight square miles of
Osaka went up in flames. On 16–17 March, three square miles of Kobe were destroyed, and on 19–20 March in a return visit to Nagoya, three more square miles were destroyed. This destructive week had killed over 120,000 Japanese civilians at the cost of only 20 B-29s lost. A month later, on 12 April, the 314th Bombardment Wing's remaining two groups, the
39th and
330th, joined in the attack on the Hodagaya Chemical Works in
Koriyama. With the addition of the 39th and 330th, the XXI Bomber Command now had three wings, twelve groups, thirty-six squadrons of 15 B-29s each at their disposal. In May, the 58th Bombardment Wing completed its move from India to Tinian, adding four more groups to the XXI Bomber Command. In April 1945, LeMay gave new orders for more incendiary raids. This time, aircraft engine factories at Musashino and Nagoya were to be hit, but urban areas in Tokyo, Nagoya, Osaka,
Kawasaki, Kobe, and
Yokohama were also to be attacked. On 7 April 153 B-29s struck the
Mitsubishi Heavy Industries aircraft-engine complex at Nagoya, destroying about 90 percent of that facility. Five days later, 93 B-29s destroyed the Nakajima factory at Musashino. The Japanese aircraft engine industry essentially ceased to exist after this time. On 13 April 327 B-29s burned out eleven more square miles of Tokyo. Seven more B-29s were lost. On 5 June, the B-29s attacked Kobe with such effectiveness that the city was crossed off the target list as not worth revisiting. By the end of the month, the six major cities on LeMay's list had all been effectively destroyed. Late May saw the arrival of the first of the 315th Bombardment Wing, whose B-29B planes were equipped with the new
AN/APQ-7 "Eagle" radar. The antenna for this radar was an 18-foot, wing-shaped unit mounted under the forward fuselage. The antenna swept a 60-degree arc along the flight path of the plane, and a higher frequency (X-band) signal gave a much-improved radarscope picture. The 315th had been trained for low-altitude, nighttime pathfinder missions. Between 26 June and 10 August, they carried out a series of 15 strikes against oil production facilities which essentially shut down the Japanese oil industry. The B-29Bs were also stripped of much defensive gunnery, adding capacity for additional incendiary or high-explosive bombs. By now, the B-29 raids were essentially unopposed by Japanese fighters. 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 by mass carpet bombing. By the end of June, the civilian population began to show signs of panic, and the Imperial Cabinet first began to consider negotiating an end to the war. However, at that time, the Japanese military was adamant about continuing on to the bitter end. In June 1945, the XX and XXI Bombardment Commands were grouped under the
U.S. Strategic Air Forces in the Pacific (USASTAF), under the command of General
Carl A. Spaatz. The history of XXI Bomber Command terminated on 16 July 1945. On that date the command was redesignated
Headquarters and Headquarters Squadron, Twentieth Air Force. This redesignation brought to an end the XXI Bomber Command as a separate establishment, as it was absorbed into the internal organizational structure of Twentieth Air Force and was placed under the command of USASTAF. ==Lineage==