Polaris A3 was generally seen as a logical extension of the FBM role established by the A1 and A2 missiles – deterrence by the threat of devastating counter-city retaliation. Although some people had favoured more emphasis on enhancing counterforce capabilities, the A3 payload was clearly ‘disoptimized’ for such a purpose, except against soft, spreadout military targets. SPO had taken care to exploit the success of the Polaris programme and to emphasize continuity and a moderate approach by retaining the Polaris name for the A3, which was almost entirely a new missile. As thoughts turned to the next generation, again this was initially thought of as another Polaris, be it A4, A3A or, as it was later known, B3.

Lockheed, keen to maintain their workload after A3, were first to suggest another generation of Polaris.