The RSD-10 Pioneer (Russian: raketa sredney dalnosti (RSD) "Pioner"; English: Medium-Range Missile "Pioneer") was an intermediate-range ballistic missile with a nuclear warhead, deployed by the Soviet Union from 1976 to 1988. Its NATO reporting name was SS-20 Saber.
Its deployment was a major cause of NATO's 'Double-Track Decision', which led to the deployment of more medium-range nuclear weapons in Western Europe. The RSD-10 was withdrawn from service under the 1987 Intermediate-Range Nuclear Forces Treaty.
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