Voyska PVO (Russian: Войска ПВО, or PVO Strany until 1981) was the air defense branch of the Soviet military. PVO is short for Protivo-Vozdushnaya Oborona or "Anti-Air Defense." Unlike Western air defense forces, PVO Strany was a branch of the military unto itself, separate from the Soviet Air Force. In the 1981 reorganization, Voyska PVO was stripped of many command and control and training assets, which were given to the Air Force. In 1998, it was merged with the Russian Air Force. Its principal role was to intercept U.S. Strategic Air Command bombers as they penetrated Soviet airspace.