The Polaris program started development in 1956, with its first flight test in 1958. In 1962, the USS Ethan Allen successfully fired a Polaris A-1 missile equipped with a live W-47 nuclear warhead against a test target during Operation Dominic.
Ongoing problems with the W-47 warhead, led to large numbers being recalled for modifications, and the U.S. Navy sought a replacement with either a larger yield or equivalent destructive power. The result was the W-58 warhead used as a 'cluster' of three for Polaris A-3, the final model. This replaced the earlier A-1 and A-2 in the US Navy and equipped the British Polaris force. The A-3 had a range extended to 4,630 km and a new weapon bay housing three Mk 2 re-entry vehicles and the new W-58 warhead of 200kT yield.
The two stages were both steered by thrust vectoring. Inertial navigation guided the missile to about a 900 m CEP, insufficient for use against hardened targets. They were mostly useful for attacking dispersed military surface targets (airfields or radar sites), clearing a pathway for heavy bombers, although in the general public perception Polaris was a strategic second-strike retaliatory weapon.
