In March 1976, the Soviet Union first deployed the RSD-10 Pioneer (called "SS-20 Saber" in the West) in its European territories, a mobile, concealable intermediate-range ballistic missile (IRBM) with a multiple independently targetable reentry vehicle (MIRV) containing three nuclear 150-kiloton warheads. The SS-20's range of was great enough to reach Western Europe from well within Soviet territory; the range was just below the Strategic Arms Limitation Talks II (SALT II) Treaty minimum range for an intercontinental ballistic missile (ICBM), . The SS-20 replaced aging Soviet systems of the SS-4 Sandal and SS-5 Skean, which were seen to pose a limited threat to Western Europe due to their poor accuracy, limited payload (one warhead), lengthy time to prepare to launch, difficulty of concealment, and a lack of mobility which exposed them to pre-emptive NATO strikes ahead of a planned attack. While the SS-4 and SS-5 were seen as defensive weapons, the SS-20 was seen as a potential offensive system.