The SS-23 short-range ballistic missile (NATO designation: Spider) was an early-1970's replacement for the 9K72 Elbrus (also known as the SS-1C "Scud B"). It was built on the 9M714 solid-fuel missile, which allowed it to be readied and fired within 30 minutes. It had a range of 310 km, and traveled at Mach 9 (6,800 mph). It was rumored that these missiles had targeting systems accurate to within 100 meters.
Using the SS-23 and the SS-21, the USSR could strike at almost all NATO airfields in Europe by the 1980's. The missile was deployed via missile trucks (similar to the Scud launchers made famous by Operation: Desert Storm), and could be moved quickly or launched from remote locations.
Under the terms of the 1987 Intermediate-Range Nuclear Forces (INF) treaty, all short- and medium-range nuclear capable launchers, rockets and warheads were banned. 239 SS-23 missiles were confirmed destroyed by 1989, as well as all known launchers.
Unfortunately, the Soviets had falsified some of the data submitted to the INF, and an estimated 120 SS-23 missiles had been supplied to three East European nations (Slovakia, Bulgaria, and East Germany). The US is now negotiating separately with these nations for the destruction of these weapons.
Data from www.fas.org.