The Soviet Air Forces (Russian: Военно-Воздушные Силы Союза Советских Социалистических Республик, Voenno-Vozdushnye Sily Soyuza Sovetskih Sotsialisticheskih Respublik, VVS SSSR; literally "Military Air Forces of the Union of Soviet Socialist Republics"; initialism VVS, sometimes referred to as the "Red Air Force") were one of the air forces of 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.