UGM-133 Trident II

The UGM-133A Trident II, or Trident D5 is a submarine-launched ballistic missile (SLBM), built by Lockheed Martin Space Systems in Sunnyvale, California, and deployed with the US and British navies. It was first deployed in March 1990, and remains in service. The Trident II Strategic Weapons System is an improved SLBM with greater accuracy, payload, and range than the Trident C-4, comprising a key element of the U.S. strategic nuclear triad and strengthening U.S. strategic deterrence. The Trident II is considered to be a durable sea-based system capable of engaging many targets. It enhances the U.S. position in strategic arms negotiation with performance and payload flexibility that can accommodate active treaty initiatives (See New START). The Trident II's increased payload allows nuclear deterrence to be accomplished with fewer submarines, and its high accuracy – approaching that of land-based missiles – enables it to be used as a first strike weapon.

Trident II missiles are carried by 14 US Ohio and 4 British Vanguard-class submarines, with 24 missiles on each Ohio class and 16 missiles on each Vanguard class. USS Tennessee (SSBN-734) was the first submarine to be armed with Trident IIs, and there have been 157 successful test flights of the D5 missile since design completion in 1989, the most recent being from the USS Kentucky (SSBN-737) in November 2015. The D5 is the sixth in a series of missile generations deployed since the sea-based deterrent program began 60 years ago. The Trident D5LE (life-extension) version will remain in service until 2042.