The Boeing B-29 Superfortress was a four-engine propeller-driven heavy bomber that was flown by the United States Military in World War II and the Korean War, and by other nations afterwards. The name "Superfortress" was derived from that of its well-known predecessor, the B-17 Flying Fortress, and carried on a series of names for Boeing-built bombers followed by the B-50, B-47 Stratojet and B-52 Stratofortress.