The United States military air campaign waged against Japan began in earnest in mid-1944 and intensified during the war's last months. While plans for attacks on Japan had been prepared prior to the Pacific War, these could not begin until the long-range B-29 Superfortress bomber was ready for combat. From June 1944 until January 1945, B-29s stationed in India staged through bases in China to make a series of nine raids on targets in western Japan, but this effort proved ineffective. The strategic bombing campaign was greatly expanded from November 1944 when bases in the Mariana Islands became available as a result of the Mariana Islands Campaign. These attacks initially attempted to target industrial facilities using high-altitude daylight "precision" bombing, which was also largely ineffective. From February 1945, the bombers switched to low-altitude night firebombing against urban areas as much of the manufacturing process was carried out in small workshops and private homes: this approach resulted in large-scale urban damage. Aircraft flying from Allied aircraft carriers and the Ryukyu Islands also frequently struck targets in Japan during 1945 in preparation for the planned invasion of Japan scheduled for October 1945. During early August 1945, the cities of Hiroshima and Nagasaki were struck and mostly destroyed by atomic bombs.