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 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. Strategic Air Forces in the Pacific operations See: United States Strategic Air Forces in the Pacific and Atomic bombings of Hiroshima and Nagasaki for expanded history A reorganization of United States military commands on 16 July 1945 placed Twentieth Air Force under the command and control of the new United States Strategic Air Forces in the Pacific. Twentieth Air Force would command B-29 wings directly based in the Mariana Islands, while the newly re-deployed Eighth Air Force would command B-29 wings based on Okinawa. This realignment was made in advance of the planned Invasion of Japan (Operation Downfall) set to begin in October 1945. XXI Bomber Command was inactivated, its organization under the direct control of Twentieth Air Force. 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. The 315th Bombardment Wing, which became operational at the beginning of July, carried out a series of strikes against oil production facilities which essentially shut down the Japanese oil industry. 509th Composite Group See: 509th Composite Group for expanded history The 509th Composite Group was deployed overseas in the spring of 1945. The 509th was initially a part of XXI Bombardment