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 raids on Japan, but this effort proved unsuccessful. 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.