SSBN

A ballistic missile submarine is a submarine deploying submarine-launched ballistic missiles (SLBMs) with nuclear warheads. The United States Navy's hull classification symbols for ballistic missile submarines are SSB and SSBN - the SS denotes submarine (or submersible ship), the B denotes ballistic missile, and the N denotes that the submarine is nuclear-powered. These submarines became a major weapon system in the Cold War because of their nuclear deterrence capability. They can fire missiles thousands of kilometers from their targets, and acoustic quieting makes them difficult to detect (see acoustic signature), thus making them a survivable deterrent in the event of a first strike and a key element of the mutual assured destruction policy of nuclear deterrence. Their deployment has been dominated by the United States and the Soviet Union / Russia, with smaller numbers in service with France, the United Kingdom, China, and most recently India.

The first sea-based missile deterrent forces were a small number of conventionally powered cruise missile submarines (SSG) and surface ships fielded by the United States and the Soviet Union in the 1950s, deploying the Regulus I missile and the Soviet P-5 Pyatyorka (SS-N-3 Shaddock), both land attack cruise missiles that could be launched from surfaced submarines. Although these forces served until 1964 and (on the Soviet side) were augmented by the nuclear-powered Project 659 (Echo I class) SSGNs, they were rapidly eclipsed by SLBMs carried by nuclear-powered ballistic missile submarines (SSBNs) beginning in 1960.

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