The Boeing B-29 Superfortress was the most advanced bomber of World War II and the most expensive weapons project of the war—costing more than the Manhattan Project. It featured a pressurized cabin for crew comfort at high altitude, remote-controlled defensive gun turrets with centralized fire control, and a 3,700-mile range that made it the only aircraft capable of striking Japan from the Marianas. The first B-29 arrived in India in April 1944. The strategic bombing campaign against Japan began in November 1944 and culminated in the firebombing of Tokyo on March 9-10, 1945, which killed an estimated 100,000 people. Two B-29s—Enola Gay and Bockscar—dropped atomic bombs on Hiroshima and Nagasaki. After the war, the B-29 served as the platform for the Soviet Tu-4 reverse-engineered copy and as the basis for the B-50 and KC-97. The last B-29 was retired from service in 1960.