The Poseidon missile was the second US Navy ballistic missile system, powered by a two-stage solid fuel rocket. It succeeded the Polaris missile beginning in 1972, bringing major advances in warheads and accuracy. It was followed by Trident I in 1979, and Trident II in 1990.
Poseidon, although longer and considerably heavier than Polaris A-3, had the same 4600 km (2500 nautical mile) range. It also had Multiple Independently Targetable Re-entry Vehicles (MIRV) and improved accuracy.