qnli question: How many B-29 bombers were airbases need for in Okinawa? sentence: The largest and bloodiest American battle came at Okinawa, as the U.S. sought airbases for 3,000 B-29 bombers and 240 squadrons of B-17 bombers for the intense bombardment of Japan's home islands in preparation for a full-scale invasion in late 1945.