The B-29 Superfortress, also known as the B-29 Super Air Fortress, was a four-engine heavy (later classified as medium after the B-36 Peacemaker entered service) propeller-driven strategic bomber designed and produced by Boeing in the United States. Primarily serving in the U.S. military, the B-29 was the main strategic bomber of the U.S. Army Air Forces during World War II and in Asian theaters such as the Korean War. Its name continued the legacy of the famous B-17 Flying Fortress strategic bomber.