The Soviet Air Forces was one of two air forces belonging to the Soviet Union. The other was the Soviet Air Defence Forces. The Air Forces were formed from components of the Imperial Russian Air Service in 1917, and faced their greatest test during World War II. The groups were also involved in the Korean War, and dissolved along with the Soviet Union itself in 1991–92. Former Soviet Air Forces' assets were subsequently divided into several air forces of former Soviet republics, including the new Russian Air Force. The "March of the Pilots" was its marching song.