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.