Subsequently, declassified material proved the USAF to be technically correct in its immediate assessment of the capabilities of the B-36 at the time of the Revolt of the Admirals. At the time, it was indeed virtually invulnerable to interception due to the great height at which it flew. However, the B-36 was a pre-World War II design and by the time it was actually operational and fully deployed to Air Force active duty bombardment wings and bombardment squadrons, the B-36 was hopelessly vulnerable to modern Soviet MiG-15 jet interceptors, aircraft that would greatly surprise U.S. officials when they later appeared over North Korea. Once engaged in the conflict in Korea that would evolve into the Korean War, the role of U.S. Air Force heavy bombers evolved into an extension of their role during World War II, support of in-theater tactical ground forces. In this instance, the USAF heavy bomber aircraft employed was the B-29 Superfortress of the second World War, while the B-36 would see no combat in Korea.