Development of the V-75 Dvina air defence missile system, designated SA-2 `Guideline' by NATO, started in 1953 as a medium to high SAM system for use against non-manoeuvring targets such as bombers. The system became operational in 1957 when the PVO-Strany formed SA-2 missile regiments of three six rail launcher battalions, with one of the initial deployments near the city of Sverdiovsk. On 1 May 1960 the Sverdiovsk units fired a total of 14 SA-2 missiles against a Lockheed U-2 high altitude reconnaissance aircraft flown by Gary Powers. The SA-2 is a two stage missile with a large solid propellant jettisonable tandem booster stage fitted with four large clipped delta stabilising fins. Towards the mid-section of the missile are four clipped delta-shaped wings with a second set of small fixed fins at the nose and a third in-line set of slightly larger moving control fins at the tail. The SA-2A/B/C models can be distinguished by the two sets of four, flush dielectric strip antennas in front and behind the forward fins.