UGM-133 Trident II in the context of "SLBM"

A submarine-launched ballistic missile (SLBM) is a ballistic missile capable of being launched from submarines. Modern variants usually deliver multiple independently targetable reentry vehicles (MIRVs), each of which carries a nuclear warhead and allows a single launched missile to strike several targets. Submarine-launched ballistic missiles operate in a different way from submarine-launched cruise missiles.

Modern submarine-launched ballistic missiles are closely related to intercontinental ballistic missiles (ICBMs), with ranges of over 5,500 kilometres (3,000 nmi), and in many cases SLBMs and ICBMs may be part of the same family of weapons.

The W88 is an American thermonuclear warhead, with an estimated yield of 475 kilotons of TNT (1,990 terajoules), and is small enough to fit on missiles with multiple independently targetable reentry vehicles (MIRV). The W88 was designed at the Los Alamos National Laboratory in the 1970s and first placed into service in 1989. The director of Los Alamos who had presided over its development described it as "the most advanced U.S. nuclear warhead". The latest version is the W88 ALT 370, the first unit of which came into production on 1 July 2021, after 11 years of development. The Trident II, a submarine-launched ballistic missile (SLBM) can be armed with up to eight W88 warheads.

Under the Manhattan Project, the United States was the first country to manufacture nuclear weapons and is the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II against Japan. In total it conducted 1,054 nuclear tests, and tested many long-range nuclear weapons delivery systems.

The United States currently deploys 1,770 warheads, mostly under Strategic Command, to its nuclear triad: Ohio-class submarines with Trident II submarine-launched ballistic missiles, silo-based Minuteman III intercontinental ballistic missiles, and B-2 Spirit and B-52 Stratofortress bombers armed with B61 and B83 bombs and AGM-86B cruise missiles. The US maintains a limited anti-ballistic missile capability via the Ground-Based Interceptor and Aegis systems. The US plans to modernize its triad with the Columbia-class submarine, Sentinel ICBM, and B-21 Raider, from 2029.

In 1952, the United Kingdom became the third country (after the United States and the Soviet Union) to develop and test nuclear weapons, and is one of the five nuclear-weapon states under the Treaty on the Non-Proliferation of Nuclear Weapons. As of 2025, the UK possesses a stockpile of approximately 225 warheads, with 120 deployed on its only delivery system, the Trident programme's submarine-launched ballistic missiles. Additionally, United States B61 nuclear bombs have been stored at RAF Lakenheath since 2025. In 2025, the UK announced plans to procure 12 F-35A aircraft capable of delivering B61s.

Since 1969, the Royal Navy has operated the continuous at-sea deterrent, with at least one ballistic missile submarine always on patrol. Under the Polaris Sales Agreement, the US supplied the UK with Polaris missiles and nuclear submarine technology, in exchange for the general commitment of these forces to NATO. In 1982, an amendment allowed the purchase of Trident II missiles, and since 1998, Trident has been the only nuclear weapons system in British service. Four Vanguard-class submarines are based at HMNB Clyde in Scotland. Each is armed with up to sixteen Trident II missiles, each carrying warheads in up to eight multiple independently targetable re-entry vehicles (MIRVs).

A multiple independently targetable reentry vehicle (MIRV) is an exoatmospheric ballistic missile payload containing several warheads, each capable of being aimed to hit a different target. The concept is almost invariably associated with intercontinental ballistic missiles carrying thermonuclear warheads, even if not strictly being limited to them. An intermediate case is the multiple reentry vehicle (MRV) missile which carries several warheads which are dispersed but not individually aimed. All nuclear-weapon states except Pakistan and North Korea are currently confirmed to have deployed MIRV missile systems.

The first true MIRV design was the Minuteman III, first successfully tested in 1968 and introduced into actual use in 1970. The Minuteman III held three smaller W62 warheads, with yields of about 170 kilotons of TNT (710 TJ) each in place of the single 1.2 megatons of TNT (5.0 PJ) W56 used on the Minuteman II. From 1970 to 1975, the United States would remove approximately 550 earlier versions of the Minuteman ICBM in the Strategic Air Command's (SAC) arsenal and replace them with the new Minuteman IIIs outfitted with a MIRV payload, increasing their overall effectiveness. The smaller power of the warheads used (W62, W78 and W87) was offset by increasing the accuracy of the system, allowing it to attack the same hard targets as the larger, less accurate, W56. The MMIII was introduced specifically to address the Soviet construction of an anti-ballistic missile (ABM) system around Moscow; MIRV allowed the US to overwhelm any conceivable ABM system without increasing the size of their own missile fleet. The Soviets responded by adding MIRV to their R-36 design, first with three warheads in 1975, and eventually up to ten in later versions. While the United States phased out the use of MIRVs in ICBMs in 2014 to comply with New START, Russia continues to develop new ICBM designs using the technology.

The Lockheed Martin Corporation is an American defense and aerospace manufacturer. It is headquartered in North Bethesda, Maryland, United States. The company was formed by the merger of Lockheed Corporation with Martin Marietta on March 15, 1995.

Lockheed Martin operates 4 divisions: Lockheed Martin Aeronautics (39% of 2024 revenues), which includes Skunk Works, the F-35 Lightning II strike fighter, the Lockheed C-130 Hercules military transport aircraft, the F-16 Fighting Falcon, and the F-22 Raptor; Lockheed Martin Missiles and Fire Control (18% of 2024 revenues), which includes the MIM-104 Patriot surface-to-air missile, the Terminal High Altitude Area Defense, the M270 Multiple Launch Rocket System, the Precision Strike Missile, the AGM-158 JASSM air-launched cruise missile, the AGM-158C LRASM anti-ship missile, the AGM-114 Hellfire, the Apache fire-control system, the Sniper Advanced Targeting Pod, Infrared search and track, and support services for special forces; Lockheed Martin Rotary and Mission Systems (24% of 2024 revenues), which includes Sikorsky Aircraft such as the Sikorsky UH-60 Black Hawk, Sikorsky HH-60 Pave Hawk, Sikorsky VH-92 Patriot, Sikorsky CH-53K King Stallion, and Sikorsky SH-60 Seahawk, the Aegis Combat System, Littoral combat ships, Freedom-class littoral combat ships, River-class destroyers, and the C2BMC missile defense program; and Lockheed Martin Space (18% of 2024 revenues), which includes the UGM-133 Trident II ballistic missile, the Orion spacecraft, the Next-Generation Overhead Persistent Infrared, GPS Block III, hypersonic weapons and transport layer programs and the Ground-Based Interceptor.

In nuclear strategy, a counterforce target is one that has a military value, such as a launch silo for intercontinental ballistic missiles, an airbase at which nuclear-armed bombers are stationed, a homeport for ballistic missile submarines, or a command and control installation.

The intent of a counterforce strategy (attacking counterforce targets with nuclear weapons) is to conduct a preemptive nuclear strike which has as its aim to disarm an adversary by destroying its nuclear weapons before they can be launched. That would minimize the impact of a retaliatory second strike. However, counterforce attacks are possible in a second strike as well, especially with more survivable submarine-launched weapons like UGM-133 Trident II. A counterforce target is distinguished from a countervalue target, which includes an adversary's population, knowledge, economic, or political resources. In short, a counterforce strike is directed against an adversary's military capabilities, while a countervalue strike is directed against an adversary's civilian-centered institutions.

The LGM-30 Minuteman is an American land-based intercontinental ballistic missile (ICBM) in service with the Air Force Global Strike Command. As of 2025, the LGM-30G (Version 3) is the only land-based ICBM in service in the United States and represents the land leg of the U.S. nuclear triad, along with the Trident II submarine-launched ballistic missile (SLBM) and nuclear weapons carried by long-range strategic bombers.

Development of the Minuteman began in the mid-1950s when basic research indicated that a solid-fuel rocket motor could stand ready to launch for long periods of time, in contrast to liquid-fueled rockets that required fueling before launch and so might be destroyed in a surprise attack. The missile was named for the colonial minutemen of the American Revolutionary War, who could be ready to fight on short notice.