Submarine-Launched Ballistic Missiles

In 1960 the first submarines incorporating a battery of solid-propellant submarine-launched ballistic missiles (SLBM) with nuclear warheads were built in the United States. Known as the Polaris missile, this weapon was capable of striking targets about 4,000 km (2,500 mi) from a submerged nuclear-fuelled ballistic-missile submarine (SSBN). In the mid-1960s a long-range, inertially guided antisubmarine missile was developed that could be launched underwater from the torpedo tubes of a submarine. In the late 1960s the Polaris missile was replaced on some submarines by Poseidon, a new longer-range SLBM, capable of carrying up to ten nuclear warheads.

The Trident I and II systems are the successors to Polaris and Poseidon. They include the new US Ohio class of nuclear submarine equipped with 24 launching tubes, each containing an intercontinental ballistic missile with a range of 7,400 km (4,600 mi). The Trident C-4 and the longer-range Trident D-5 SLBM have replaced Polaris and Poseidon on 17 US ballistic missile submarines.

Britain has 2 SSBNs, each carrying 16 Vanguard-class US-produced Trident D-5 missiles. The third British Trident submarine was launched in 1995, scheduled to enter service in 1998. The fourth is due for launch in 1998. While the Trident I (or C-4) missile can deliver eight independently targetable 100-kiloton nuclear warheads, Trident II (or D-5) carries some ten 475-kiloton warheads and has a range of 11,300 km (7,000 mi). Britain's Vanguard submarines have been built to carry Trident II with British-made warheads. All tactical (short-range) nuclear warheads have been withdrawn from ships and submarines.