Sea-Launched Ballistic Missiles (SLBMS)

In the event of a nuclear war or other threat to U.S. national security, missiles capable of being launched from nuclear submarines. Nuclear submarines form one-third of the strategic nuclear triad, along with land-based missiles and bombers. The advantage of launching missiles from submarines is that the missiles may be dispersed across a wide area, making it essentially impossible to destroy them all at once. The disadvantage is that communication with nuclear submarines enables the detection of the submarine's location; also submarine-launched missiles are less accurate than those launched from land.

Sea-launched ballistic missiles are carried by Ohio class, Trident submarines, the largest submarines deployed by the U.S. Navy, second in size only to Russian Typhoon submarines. These submarines, specifically designed for extended patrols at sea, are equipped with Trident Intercontinental Ballistic Missiles (ICBMs), which are designated as sea-launched ballistic missiles (SLBMs).

Missile launch from a submarine occurs below the ocean's surface. However, the missile never makes contact with the water because it is surrounded by a bubble of gas. Gas pressure ejects the missile from its launch tube within the submarine. The first Trident was deployed in 1979, and the first Trident II in 1990; the Trident II is expected to be in service until the year 2020.