Developed by the Soviet Union, the SA-2 has been the most widely used air defense missile in the world. In the Soviet Union it was called the Dvina; in the West it was known by its NATO code name, SA-2 Guideline (SA meaning surface-to-air). SA-2s became operational in 1959 and were acquired by all Soviet client states. In 1960 an SA-2 downed the American U-2 spy plane piloted by Francis Gary Powers.The SA-2 had a solid-fuel booster and a liquid-fuel second stage. Many countries made their own versions of the missile. This one, meant for export, is mounted on a transporter and required a separate launcher. SA-2s are still in use today. This object was donated to the Smithsonian in 1985 by the U.S. Navy.