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Arsenal and Missile Types
NPT Nuclear Weapon State
Arsenal Size
- Total warheads: Approximately 225
- Operationally available warheads: Up to 120
- Government announced in 2021 intention to increase stockpile ceiling to up to 260 warheads (increased from its 2010 commitment to a ceiling of 180 warheads)
Weapon System
- Four Vanguard-class nuclear-powered ballistic missile submarines (SSBNs), armed with Trident II D5 submarine-launched ballistic missiles (SLBMs). The United Kingdom’s policy of Continuous At Sea Deterrence (CASD) requires that one Vanguard-class submarine be on patrol at all times.
- New Dreadnought-class SSBNs planned to replace the Vanguard-class fleet starting in the early 2030s.
Capabilities and Developments
Military Fissile Material Stockpile
- Plutonium: 3.2 metric tons
- Highly Enriched Uranium (HEU): 22 metric tons
Commitments and Policies
Disarmament and Commitments to Reduce Arsenal Size
- Legal obligation to pursue global disarmament under Article VI of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).
- The UK is the only nuclear weapon state (NWS) with a single weapon system (the Trident II D5 SLBM) and has the smallest nuclear arsenal of the five official NWS.
- Since 2010, the UK has decreased the number of warheads on each submarine from 48 to 40, decreased the requirement for available warheads from 160 to 120, and decreased the number of operational missiles on each submarine to 8.
Future Commitment
- Prioritizes the negotiation of a verifiable Fissile Material Cut-Off Treaty (FMCT) without preconditions. The treaty should not cover existing stockpiles.
Nuclear Weapons Policies
- Maintains the long-term goal of a world free of nuclear weapons and is viewed by many experts as the most successful nuclear weapon state in creating a minimum deterrent. However, the government will continue its submarine-based ballistic missile nuclear deterrence capability as long as it feels is necessary given current global security considerations.
- Committed to reducing its arsenal size, but the UK is pursuing modernization of its warhead design, life extension of the Trident II D5 missiles, and a new SSBN fleet to replace the aging Vanguard submarines and maintain the CASD policy.
- The UK joined all other nuclear weapons possessing states in boycotting the 2017 Nuclear Ban Treaty negotiations at the UN General Assembly. The UK has no plans to join the Treaty on the Prohibition of Nuclear Weapons (TPNW).
Nuclear Testing
- Observed nuclear testing moratorium since 1991
- Signed and ratified the Comprehensive Nuclear Test Ban Treaty (CTBT).
- Party to the Partial Nuclear Test Ban Treaty (PTBT), which bans nuclear tests in the atmosphere, in outer space and underwater.
Use of Nuclear Weapons
- Has declared it will only use nuclear weapons in “extreme circumstances of self defence, including the defence of NATO allies,” but remains “deliberately ambiguous” on the extent to which the country will use nuclear weapons in a time of crisis.
- Negative Security Assurances to Nuclear-Weapon-Free Zone (NWFZ) treaty members: Committed not to use nuclear weapons against members of the Tlatelolco, Rarotonga, and Pelindaba treaties by ratifying protocols of these treaties.
- Signed and ratified the Central Asian NWFZ protocols. Agreed on language for the P5 Protocol to the SE Asian NWFZ (Bangkok Treaty) but postponed signing the treaty.
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Nuclear Disarmament Belarus
Nuclear Disarmament Belgium
Nuclear Disarmament China
Nuclear Disarmament France
Nuclear Disarmament Germany
Nuclear Disarmament India
Nuclear Disarmament Israel
Nuclear Disarmament Italy
Nuclear Disarmament Kazakhstan
Nuclear Disarmament NATO
Nuclear Disarmament North Korea
Nuclear Disarmament Netherlands
Nuclear Disarmament Russia
Nuclear Disarmament South Africa
Nuclear Disarmament Turkey
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Nuclear Disarmament Netherlands
Information and analysis of nuclear weapons disarmament proposals and progress in the Netherlands
Nuclear Disarmament Turkey
The Nuclear Disarmament Resource Collection contains information and analysis of nuclear weapons disarmament proposals and progress worldwide, including detailed coverage of disarmament progress in countries who either possess or host other countries' nuclear weapons on their territories.
Nuclear Disarmament NATO
Information and analysis of nuclear weapons disarmament proposals and progress in NATO member states
Glossary
- Treaty on the Non-Proliferation of Nuclear Weapons (NPT)
- The NPT: Signed in 1968, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the most widely adhered-to international security agreement. The “three pillars” of the NPT are nuclear disarmament, nonproliferation, and peaceful uses of nuclear energy. Article VI of the NPT commits states possessing nuclear weapons to negotiate in good faith toward halting the arms race and the complete elimination of nuclear weapons. The Treaty stipulates that non-nuclear-weapon states will not seek to acquire nuclear weapons, and will accept International Atomic Energy Agency safeguards on their nuclear activities, while nuclear weapon states commit not to transfer nuclear weapons to other states. All states have a right to the peaceful use of nuclear energy, and should assist one another in its development. The NPT provides for conferences of member states to review treaty implementation at five-year intervals. Initially of a 25-year duration, the NPT was extended indefinitely in 1995. For additional information, see the NPT.
- Ballistic missile
- A delivery vehicle powered by a liquid or solid fueled rocket that primarily travels in a ballistic (free-fall) trajectory. The flight of a ballistic missile includes three phases: 1) boost phase, where the rocket generates thrust to launch the missile into flight; 2) midcourse phase, where the missile coasts in an arc under the influence of gravity; and 3) terminal phase, in which the missile descends towards its target. Ballistic missiles can be characterized by three key parameters - range, payload, and Circular Error Probable (CEP), or targeting precision. Ballistic missiles are primarily intended for use against ground targets.
- SSBN
- Ship, Submersible, Ballistic, Nuclear: A hull classification for a submarine capable of launching a ballistic missile. The "N", or nuclear, refers to the ship's propulsion system. SSBN's are generally reserved for strategic vessels, as most submarine launched ballistic missiles carry nuclear payloads. A non-strategic vessel carries the designation SSN, or attack submarine.
- Submarine-launched ballistic missile (SLBM)
- SLBM: A ballistic missile that is carried on and launched from a submarine.
- Plutonium (Pu)
- Plutonium (Pu): A transuranic element with atomic number 94, produced when uranium is irradiated in a reactor. It is used primarily in nuclear weapons and, along with uranium, in mixed-oxide (MOX) fuel. Plutonium-239, a fissile isotope, is the most suitable isotope for use in nuclear weapons.
- Highly enriched uranium (HEU)
- Highly enriched uranium (HEU): Refers to uranium with a concentration of more than 20% of the isotope U-235. Achieved via the process of enrichment. See entry for enriched uranium.
- Disarmament
- Though there is no agreed-upon legal definition of what disarmament entails within the context of international agreements, a general definition is the process of reducing the quantity and/or capabilities of military weapons and/or military forces.
- Treaty on the Non-Proliferation of Nuclear Weapons (NPT)
- The NPT: Signed in 1968, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the most widely adhered-to international security agreement. The “three pillars” of the NPT are nuclear disarmament, nonproliferation, and peaceful uses of nuclear energy. Article VI of the NPT commits states possessing nuclear weapons to negotiate in good faith toward halting the arms race and the complete elimination of nuclear weapons. The Treaty stipulates that non-nuclear-weapon states will not seek to acquire nuclear weapons, and will accept International Atomic Energy Agency safeguards on their nuclear activities, while nuclear weapon states commit not to transfer nuclear weapons to other states. All states have a right to the peaceful use of nuclear energy, and should assist one another in its development. The NPT provides for conferences of member states to review treaty implementation at five-year intervals. Initially of a 25-year duration, the NPT was extended indefinitely in 1995. For additional information, see the NPT.
- Nuclear-weapon states (NWS)
- NWS: As defined by Article IX, paragraph 3 of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the five states that detonated a nuclear device prior to 1 January 1967 (China, France, the Soviet Union, the United Kingdom, and the United States). Coincidentally, these five states are also permanent members of the UN Security Council. States that acquired and/or tested nuclear weapons subsequently are not internationally recognized as nuclear-weapon states.
- Fissile Material Cut-off Treaty (FMCT)
- The Fissile Material Cut-off Treaty us currently under discussion in the Conference on Disarmament (CD) to end the production of weapons-usable fissile material (highly enriched uranium and plutonium) for nuclear weapons. For additional information, see the FMCT.
- Deterrence
- The actions of a state or group of states to dissuade a potential adversary from initiating an attack or conflict through the credible threat of retaliation. To be effective, a deterrence strategy should demonstrate to an adversary that the costs of an attack would outweigh any potential gains. See entries for Extended deterrence and nuclear deterrence.
- United Nations General Assembly
- The UN General Assembly is the largest body of the United Nations. It includes all member states, but its resolutions are not legally binding. It is responsible for much of the work of the United Nations, including controlling finances, passing resolutions, and electing non-permanent members of the Security Council. It has two subsidiary bodies dealing particularly with security and disarmament: the UN General Assembly Committee on Disarmament and International Security (First Committee); and the UN Disarmament Commission. For additional information, see the UNGA.
- Ratification
- Ratification: The implementation of the formal process established by a country to legally bind its government to a treaty, such as approval by a parliament. In the United States, treaty ratification requires approval by the president after he or she has received the advice and consent of two-thirds of the Senate. Following ratification, a country submits the requisite legal instrument to the treaty’s depository governments Procedures to ratify a treaty follow its signature.
See entries for Entry into force and Signature. - Comprehensive Nuclear-Test-Ban Treaty (CTBT)
- The CTBT: Opened for signature in 1996 at the UN General Assembly, the CTBT prohibits all nuclear testing if it enters into force. The treaty establishes the Comprehensive Test Ban Treaty Organization (CTBTO) to ensure the implementation of its provisions and verify compliance through a global monitoring system upon entry into force. Pending the treaty’s entry into force, the Preparatory Commission of the CTBTO is charged with establishing the International Monitoring System (IMS) and promoting treaty ratifications. CTBT entry into force is contingent on ratification by 44 Annex II states. For additional information, see the CTBT.
- Partial Test Ban Treaty (PTBT)
- The PTBT: Also known as the Limited Test Ban Treaty (LTBT), the Treaty Banning Nuclear Weapons Tests in the Atmosphere, in Outer Space and Under Water prohibits nuclear weapons tests "or any other nuclear explosion" in the atmosphere, in outer space, and under water. While the treaty does not ban tests underground, it does prohibit nuclear explosions in this environment if they cause "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control" the explosions were conducted. The treaty is of unlimited duration. For additional information, see the PTBT.
- North Atlantic Treaty Organization (NATO)
- The North Atlantic Treaty Organization is a military alliance that was formed in 1949 to help deter the Soviet Union from attacking Europe. The Alliance is based on the North Atlantic Treaty, which was signed in Washington on 4 April 1949. The treaty originally created an alliance of 10 European and two North American independent states, but today NATO has 28 members who have committed to maintaining and developing their defense capabilities, to consulting on issues of mutual security concern, and to the principle of collective self-defense. NATO is also engaged in out-of-area security operations, most notably in Afghanistan, where Alliance forces operate alongside other non-NATO countries as part of the International Security Assistance Force (ISAF). For additional information, see NATO.
- Negative security assurances
- A pledge by a nuclear weapon state that it will not use nuclear weapons against a non-nuclear weapon state. Some states have policies that allow for the use of nuclear weapons if attacked with other WMD by a non-nuclear weapon state. See entry for Positive security assurances.
- Nuclear-Weapon-Free Zone (NWFZ)
- NWFZ: A geographical area in which nuclear weapons may not legally be built, possessed, transferred, deployed, or tested.
- Treaty of Tlatelolco
- The Treaty of Tlatelolco: This treaty, opened for signature in February 1967, created a nuclear-weapon-free zone in Latin America and the Caribbean. The Treaty of Tlatelolco was the first international agreement that aimed to exclude nuclear weapons from an inhabited region of the globe. The member states accept the application of International Atomic Energy Agency safeguards on all their nuclear activities. The treaty also establishes a regional organization, the Agency for the Prohibition of Nuclear Weapons in Latin America (OPANAL), to supervise treaty implementation and ensure compliance with its provisions. For additional information, see the LANWFZ.
- Treaty of Rarotonga
- Treaty of Rarotonga: The Treaty on the South Pacific Nuclear-Weapon-Free Zone (SPNWFZ) prohibits the testing, manufacturing, acquiring, and stationing of nuclear explosive devices on any member's territory. The treaty also prohibits the dumping of radioactive wastes into the sea. In addition, the treaty required all parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities. For additional information, see the SPNWFZ.
- Treaty of Pelindaba
- Treaty of Pelindaba: The Treaty on the African Nuclear-Weapon-Free-Zone was opened for signature in Cairo in April 1996. The treaty prohibits the research, development, manufacturing, stockpiling, acquisition, testing, possession, control, and stationing of nuclear explosive devices on any member’s territory. The treaty also prohibits the dumping of radioactive waste originating from outside the continent within the region. In addition, the treaty requires parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities. The treaty also provides for the establishment of the African Commission on Nuclear Energy (AFCONE), which supervises treaty implementation and ensures compliance with its provisions. For additional information, see the ANWFZ.
- Ratification
- Ratification: The implementation of the formal process established by a country to legally bind its government to a treaty, such as approval by a parliament. In the United States, treaty ratification requires approval by the president after he or she has received the advice and consent of two-thirds of the Senate. Following ratification, a country submits the requisite legal instrument to the treaty’s depository governments Procedures to ratify a treaty follow its signature.
See entries for Entry into force and Signature. - Central Asia Nuclear-Weapon-Free Zone (CANWFZ)
- The Central Asia Nuclear-Weapons-Free-Zone (CANWFZ) includes all five Central Asian states: Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The foreign ministers of the five countries signed the treaty establishing the zone on 8 September 2006 at the former Soviet nuclear test site in Semipalatinsk, Kazakhstan. The treaty entered into force on 21 March 2009. For additional information, see the CANWFZ.
- P-5
- P-5: The five permanent members of the United Nations Security Council: China, France, the Russian Federation, the United Kingdom, and the United States.
- Southeast Asian Nuclear-Weapon-Free-Zone (SEANWFZ)
- The Treaty on the Southeast Asian Nuclear-Weapon-Free-Zone (SEANWFZ) prohibits the development, manufacture, acquisition, or testing of nuclear weapons anywhere within the region. It also prohibits the transport of nuclear weapons through the region, as well as the dumping at sea, discharging into the atmosphere, or burying on land of any radioactive material or waste. In addition, the treaty requires all parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities. For additional information, see the SEANWFZ.
- Treaty of Bangkok
- Treaty of Bangkok: The Treaty on the Southeast Asian Nuclear-Weapon-Free-Zone prohibits the development, manufacture, acquisition, or testing of nuclear weapons anywhere within the region. It also prohibits the transport of nuclear weapons through the region, as well as the dumping at sea, discharging into the atmosphere, or burying on land of any radioactive material or waste. In addition, the treaty requires all parties to apply International Atomic Energy Agency safeguards to all their peaceful nuclear activities. For additional information, see the SEANWFZ.
Sources
- Joanne Adamson, “Statement: Cluster II – Non-Proliferation,” 2012 Preparatory Committee for the Nuclear Non-Proliferation Treaty, May 7, 2012, www.reachingcriticalwill.org.
- Joanne Adamson, “Statement on Fissile Material Cutoff Treaty,” Council on Disarmament, March 12, 2013, www.reachingcriticalwill.org.
- Shubhra Chaturvedi, “Southeast Asian Nuclear Weapon Free Zone Treaty: What’s Holding It Up?” International Peace and Conflict Studies, July 31, 2012, www.ipcs.org.
- CTBTO Preparatory Commission, “Status of Signature and Ratification,” www.ctbto.org.
- “Nuclear Weapon Free Zone (NWFZ) Clearinghouse,” James Martin Center for Nonproliferation Studies, www.nonproliferation.org.
- “Inventory of International Nonproliferation Organizations & Regimes,” James Martin Center for Nonproliferation Studies, www.nonproliferation.org.
- Hans M. Kristensen and Matt Korda, “United Kingdom nuclear weapons, 2021,” Bulletin of the Atomic Scientists 77, No. 3 (2021), pp. 153-158.
- Hans M. Kristensen, Matt Korda, Eliana Johns, Mackenzie Knight, and Kate Kohn, “Status of World Nuclear Forces,” Federation of American Scientists, March 29, 2024, www.fas.org.
- “Main Committee I Statement,” Report by Mr. Guy Pollard, Deputy Permanent Representative of the United Kingdom to the Conference on Disarmament, 2015 Review Conference of the Treaty on Non-Proliferation of Nuclear Weapons, April 27-May 22, 2015.
- “United Kingdom,” International Campaign to Abolish Nuclear Weapons, www.icanw.org.
- “The UK’s Nuclear Deterrent: What You Need to Know,” Defense Nuclear Organisation, March 28, 2024, www.gov.uk.
- United Nations, “Treaty banning nuclear weapon tests in the atmosphere, in outer space and under water,” https://treaties.un.org.
- “Countries: United Kingdom,” International Panel on Fissile Materials, April 13, 2024, https://fissilematerials.org.
- “Fissile material stocks,” International Panel on Fissile Materials, April 13, 2024, https://fissilematerials.org.