Fact Sheet

South Korea Overview

South Korea Overview

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South Korea, officially the Republic of Korea (ROK), has maintained a bilateral security alliance with the United States since the Korean War (1950-1953). The ROK abandoned its nuclear weapons efforts in the 1970s, and is engaging in diplomatic efforts with North Korea and the United States to attempt to denuclearize the Korean peninsula. South Korea is a party to all major nonproliferation treaties and regimes, possesses ballistic and cruise missiles, and cooperates with the United States on missile defense.


South Korea first became interested in nuclear technology in the 1950s, but did not begin construction of its first nuclear power plant until 1971. [1] Changes in the international security environment influenced South Korea's decision to begin a nuclear weapons program in the early 1970s, but the ROK abandoned the effort under significant pressure from the United States. [2] In April 1975, South Korea signed the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). [3] South Korea is also a party to the Comprehensive Nuclear Test Ban Treaty (CTBT) and is a member of the Nuclear Suppliers Group and the Zangger Committee. [4]

The United States deployed tactical nuclear weapons in South Korea from 1958 until 1991. [5] Afterward, South Korea focused its diplomatic efforts on keeping the Korean peninsula free of nuclear weapons. In January 1992, North and South Korea signed the Joint Declaration on the Denuclearization of the Korean Peninsula. In this agreement, North Korea and South Korea agreed not "to test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons," and not to "possess nuclear reprocessing and uranium enrichment facilities." [6] However, both sides failed to implement the agreement's provisions relating to a bilateral inspections regime. [7] Despite North Korea’s violations of the Joint Declaration, including its multiple nuclear weapons tests, South Korea has never officially renounced its obligations under the declaration, and has called on the North to abide by the agreement. [8]

Beginning in 2003, South Korea participated in the Six-Party Talks, aimed at ending the nuclear crisis on the Korean Peninsula, until North Korea withdrew in 2009 over disagreements with the UN Security Council. [9] At the April 2018 Inter-Korean Summit, North and South Korean heads of state declared their aspiration for a “complete denuclearization” of the Korean Peninsula, echoing sentiments expressed 26 years earlier. [10]

South Korea’s civil nuclear sector is highly developed; 23 nuclear reactors supply a third of the country’s electricity. Two additional reactors are under construction. [11] Following President Moon Jae-in’s June 2017 announcement that South Korea would limit its use of nuclear energy moving forward, South Korea froze all ongoing construction and scrapped plans for future reactors. [12] Facing considerable public opposition, the Moon government restarted work on the two partially completed nuclear reactors in October 2017, but still plans to phase out nuclear power over the coming decades. [13]


South Korea ratified the Biological and Toxin Weapons Convention (BTWC) in June 1987 and joined the Australia Group in October 1995. [14] Although South Korea possesses a well-developed pharmaceutical and biotechnology infrastructure, it has committed to pursue only defensive BW research and development. [15]


South Korea ratified the Chemical Weapons Convention (CWC) in April 1997. [16] At that time, South Korea reportedly confidentially declared possession of several thousand metric tons of chemical warfare agents and one chemical weapons (CW) production facility to the Organization for the Prohibition of Chemical Weapons (OPCW). Neither the OPCW nor South Korea has publicly acknowledged this declaration. The South Korean government has maintained a high level of secrecy regarding its previous chemical weapons activities, reportedly requiring the OPCW to refer to it in all documents as "another state party" or "an unnamed state party." However, media reports indicate that pursuant to its CWC obligations, the South Korean military built and operated a CW destruction facility to eliminate all CW munitions at a site in Yeongdong Chungcheong. [17]

Under the CWC, South Korea was obligated to eliminate its CW stockpile by April 2007. South Korea requested an extension on that deadline from the OPCW, reportedly citing a number of technical difficulties in the operation of its destruction facility. South Korea reportedly completed the destruction of its entire chemical weapons stockpile in July 2008, becoming the second CWC member to do. [18]

In the wake of the shelling of Yeonpyeong Island in November 2010, the South Korean government and the National Emergency Management Agency (NEMA) began to equip civilian facilities — such as subway stations — with gas and oxygen masks, as well as oxygen tanks, to be used in case of chemical attacks by North Korea. [19] Additionally, the U.S. chemical warfare battalion, which previously left South Korea in 2004, was redeployed to the Korean peninsula in 2013. [20]


South Korea began developing missiles in the early 1970s, and successfully tested its first missile system NHK-1 (aka Baekgom-1), in September 1978. Currently, South Korea deploys a series of short-range ballistic missiles and several types of cruise missiles. South Korea joined the Missile Technology Control Regime (MTCR) in March 2001. [21] Until 2017, South Korea’s missile program was constrained by a series of bilateral agreements with the United States, which imposed range and payload restrictions on its indigenous missiles. In response to North Korea’s Unha-3 rocket launch in 2012, the United States and South Korea issued a new memorandum allowing South Korea to develop missiles ranging up to 800 kilometers, far enough to strike targets anywhere in North Korea. [22] In response to North Korean missile and nuclear tests in 2017, the United States and South Korea also agreed to lift restrictions on missile payloads. [23] In the 1990s, South Korea began development of a space program, including a space-launch vehicle (SLV). After numerous delays, South Korea successfully launched the two-stage KSLV-1 rocket on August 25, 2009. South Korea successfully placed a satellite into orbit in January 2013. [24]

In early 2017, the United States deployed two Terminal High Altitude Aerial Defense (THAAD) systems to South Korea, supplementing existing deployments of Patriot and Aegis missile defense systems in the region. [25] Despite a campaign pledge to remove the missiles, the Moon administration decided to continue THAAD deployments following North Korea’s ICBM tests in 2017. [26]

[1] Ha Yeong-seon, 한반도의 핵무기와 세계질서 [Nuclear Weapons on the Korean Peninsula and World Order] (Seoul: Nanam, 1991).
[2] Larry A. Niksch, “U.S. Troop Withdrawal from South Korea: Past Shortcomings and Future Prospects,” Asian Survey 21 No. 3 (March 1981) pp. 325-34; Michael J. Siler, “U.S. Nuclear Nonproliferation Policy in The Northeast Asian Region During the Cold War: The South Korean Case,” East Asia 16, No. 3-4 (September 1998), pp 41-86; Etel Solingen, Nuclear Logics: Contrasting Paths in East Asia and the Middle East, (Princeton: The Princeton University Press, 2009) pp. 64 – 78.
[3] Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, 9 November 2004, www.nonproliferation.org.
[4] United Nations Office for Disarmament Affairs, "Status of Multilateral Arms Regulation and Disarmament Agreements," www.un.org; "Who are the Current NSG Participants?" Nuclear Suppliers Group, www.nuclearsuppliersgroup.org; "Members," Zangger Committee, 13 January 2010, www.zanggercommittee.org.
[5] ] Hans Kristensen and Robert S. Norris, “A History of US Nuclear Weapons in South Korea,” Bulletin of the Atomic Scientists 73 No. 6 (October 2017) pp. 349-357; Roh Tae Woo, "President Roh Tae Woo's Declaration of Non-Nuclear Korean Peninsula Peace Initiatives," 8 November 1991, www.fas.org.
[6] "Korean Denuclearization Agreement," 20 January 1992, via: www2.law.columbia.edu.
[7] B.K. Kim, "Step-by-Step Confidence Building on the Korean Peninsula: Where Do We Start?" Institute for Science and International Security, Building Nuclear Confidence on the Korean Peninsula: Proceedings from the 23-24 July 2001 Workshop, p. 154, www.isis-online.org.
[8] "North Korea's Nuclear Tests," BBC, 12 February 2013, www.bbc.com; "Text of the Joint Statement," The New York Times, 19 September 2005, via: www.nytimes.com.
[9] Xiaodon Lian, "The Six Party Talks at a Glance," Arms Control Association, May 2012, www.armscontrol.org; Hyun-ju Ock, "No Six Party Talks without Progress: Korean Diplomat," The Korea Times, 16 June 2014, www.koreaherald.com; Mark Landler, “North Korea Says It Will Halt Talks and Restart Its Nuclear Program,” The New York Times, 14 April 2009, nytimes.com.
[10] “Full Text of Declaration Issued at Inter-Korean Summit,” Yonhap News, 27 April 2018, english.yonhapnews.co.kr.
[11] International Atomic Energy Agency, "Korea, Republic of," Power Reactor Information System Database, July 2017, http://pris.iaea.org.
[12] Jane Chung, “South Korea to resume building two new nuclear reactors, but scraps plans for 6 others,” Reuters, 24 October 2017, www.reuters.com.
[13] United Nations Office for Disarmament Affairs, "Status of Multilateral Arms Regulation and Disarmament Agreements," www.un.org; "Australia Group Participants," www.australiagroup.net.
[14] Bureau of Arms Control, Verification, and Compliance, “2018 Report on Adherence and Compliance with Arms Control, Nonproliferation, and Disarmament Agreements and Commitments,” U.S. Department of State, April 2018, state.gov.
[15] Republic of Korea Ministry of National Defense, "2006 Defense White Paper," May 2007, p. 26, www.mnd.go.kr; Republic of Korea Ministry of National Defense, "2010 Defense White Paper," December 2010, www.mnd.go.kr; Republic of Korea Ministry of National Defense, "2012 Defense White Paper," December 2012, www.mnd.go.kr; Republic of Korea Ministry of National Defense, “2016 Defense White Paper,” 31 December 2016, www.mnd.go.kr.
[16] Organisation for the Prohibition of Chemical Weapons, "Member State – Republic of Korea," www.opcw.org.
[17] "Report: Korean Army Built Factory to Destroy Chemical Weapons," Deutsche Presse-Agentur, 9 May 2000.
[18] Chris Schneidmiller, "South Korea Completes Chemical Weapons Disposal," Global Security Newswire, 17 October 2008, www.nti.org.
[19] Lee Dong-young, "화생방 공격에도 6시간 '안전'… 500파운드 폭탄 터져도 '거뜬'," [6 Hours of Safety Even in the Case of Chemical Attacks… Safe Even with the Explosion of 500-pound Bomb], Dong-A Ilbo, 4 October 2011, http://news.donga.com.
[20] "U.S. Chemical Warfare Battalion to Return to Korea," Chosun Ilbo, 8 October 2012, http://english.chosun.com; Jon Rabiroff, "Chemical Weapon Unit Back in South Korea: Timing Coincidental," Stars and Stripes, 4 April 2013, www.stripes.com; Second Infantry Division, “23rd Chemical Battalion,” U.S. Army, 23 February 2018, www.2id.korea.army.mil.
[21] Lee Min-jung, "탄도미사일 사거리 연장되나 [Will the Missile Range be Extended for South Korea?]" EDAILY, 13 June 2012, www.edaily.co.kr; Missile Technology Control Regime, "MTCR Partners," www.mtcr.info.
[22] Choe Sang-Hun, “U.S. Agrees to Let South Korea Extend Range of Ballistic Missiles,” The New York Times, 7 October 2012, www.nytimes.com.
[23] U.S. Executive Office of the President, “Joint Press Release by the United States of America and the Republic of Korea” Press release, U.S. Executive Office, 8 November 2017, www.whitehouse.gov.
[24] Tong-hyung Kim, "Naro Rocket Blows Up in Midair," The Korea Times, 10 June 2010, www.koreatimes.co.kr; Jung-yoon Choi and Barbara Demick, "South Korea Launches Satellite into Orbit," The Los Angeles Times, 30 January 2013, www.latimes.com.
[25] Ian E. Rinehart, Steven A. Hildreth, and Susan V. Lawrence, “Ballistic Missile Defense in the Asia-Pacific Region: Cooperation And Opposition,” CRS Report 7-5700, Congressional Research Service, 3 April 2015.
[26] Michael Elleman, "North Korea Launches Another Large Rocket: Consequences and Options," 38 North, 10 February 2016; Alex Johnson, Stella Kim, Courtney Kube, “U.S. Begins Shipping Controversial Anti-Missile System to South Korea,” NBC News, 7 March 2017, www.nbcnews.com.

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Bilateral: Negotiations, arrangements, agreements, or treaties that affect or are between two parties—and generally two countries.
Nonproliferation: Measures to prevent the spread of biological, chemical, and/or nuclear weapons and their delivery systems. See entry for Proliferation.
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.
Cruise missile
An unmanned self-propelled guided vehicle that sustains flight through aerodynamic lift for most of its flight path. There are subsonic and supersonic cruise missiles currently deployed in conventional and nuclear arsenals, while conventional hypersonic cruise missiles are currently in development. These can be launched from the air, submarines, or the ground. Although they carry smaller payloads, travel at slower speeds, and cover lesser ranges than ballistic missiles, cruise missiles can be programmed to travel along customized flight paths and to evade missile defense systems.
Nuclear power plant
Nuclear power plant: A facility that generates electricity using a nuclear reactor as its heat source to provide steam to a turbine generator.
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.
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.
Nuclear Suppliers Group (NSG)
The NSG was established in 1975, and its members commit themselves to exporting sensitive nuclear technologies only to countries that adhere to strict non-proliferation standards. For additional information, see the NSG.
Zangger Committee (ZC)
A group of 35 nuclear exporting states established in 1971 under the chairmanship of Claude Zangger of Switzerland. The purpose of the committee is to maintain a "trigger list" of: (1) source or special fissionable materials, and (2) equipment or materials especially designed or prepared for the processing, use, or production of special fissionable materials. Additionally, the committee has identified certain dual-use technologies as requiring safeguarding when they are supplied to non-nuclear weapon states. These include explosives, centrifuge components, and special materials. The Zangger Committee is an informal arrangement, and its decisions are not legally binding upon its members. For more information see the Zangger Committee
Tactical nuclear weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-range missiles, deployed for use in battlefield operations.
Joint Declaration on the Denuclearization of the Korean Peninsula
Joint Declaration on the Denuclearization of the Korean Peninsula: On 20 January 1992, both North and South Korea signed the Joint Declaration on the Denuclearization of the Korean Peninsula, whereby both states agreed not to "test, produce, receive, possess, store, deploy or use nuclear weapons; to use nuclear energy only for peaceful purposes; and not to possess facilities for nuclear reprocessing or uranium enrichment." The declaration entered into force on 19 February 1992. In order to implement the declaration, the two Koreas established the South-North Joint Nuclear Control Commission (JNCC). However, as the result of revelations about North Korea's nuclear program and failure to reach agreement on the reciprocal inspection regime, implementation has been stalled since 1993. For additional information, see the Joint Declaration on the Denuclearization of the Korean Peninsula.
The positioning of military forces – conventional and/or nuclear – in conjunction with military planning.
Reprocessing: The chemical treatment of spent nuclear fuel to separate the remaining usable plutonium and uranium for re-fabrication into fuel, or alternatively, to extract the plutonium for use in nuclear weapons.
Enriched uranium
Enriched uranium: Uranium with an increased concentration of the isotope U-235, relative to natural uranium. Natural uranium contains 0.7 percent U-235, whereas nuclear weapons typically require uranium enriched to very high levels (see the definitions for “highly enriched uranium” and “weapons-grade”). Nuclear power plant fuel typically uses uranium enriched to 3 to 5 percent U-235, material that is not sufficiently enriched to be used for nuclear weapons.
United Nations Security Council
United Nations Security Council: Under the United Nations Charter, the Security Council has primary responsibility for maintaining international peace and security. The Council consists of fifteen members, five of which—China, France, Russia, the United Kingdom, and the United States—are permanent members. The other ten members are elected by the General Assembly for two-year terms. The five permanent members possess veto powers. For additional information, see the UNSC.
Nuclear reactor
Nuclear reactor: A vessel in which nuclear fission may be sustained and controlled in a chain nuclear reaction. The varieties are many, but all incorporate certain features, including: fissionable or fissile fuel; a moderating material (unless the reactor is operated on fast neutrons); a reflector to conserve escaping neutrons; provisions of removal of heat; measuring and controlling instruments; and protective devices.
Nuclear energy
Nuclear energy: The energy liberated by a nuclear reaction (fission or fusion), or by radioactive decay.
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.
Biological and Toxin Weapons Convention (BTWC)
The BTWC: The Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction (BTWC) prohibits the development, production, or stockpiling of bacteriological and toxin weapons. Countries must destroy or divert to peaceful purposes all agents, toxins, weapons, equipment, and means of delivery within nine months after the entry into force of the convention. The BTWC was opened for signature on April 10, 1972, and entered into force on March 26, 1975. In 1994, the BTWC member states created the Ad Hoc Group to negotiate a legally binding BTWC Protocol that would help deter violations of the BTWC. The draft protocol outlines a monitoring regime that would require declarations of dual-use activities and facilities, routine visits to declared facilities, and short-notice challenge investigations. For additional information, see the BTWC.
Australia Group (AG)
Australia Group (AG): Established in 1985 to limit the spread of chemical and biological weapons (CBW) through export controls on chemical precursors, equipment, agents, and organisms. For additional information, see the Australia Group.
Chemical Weapons Convention (CWC)
The Chemical Weapons Convention (CWC) requires each state party to declare and destroy all the chemical weapons (CW) and CW production facilities it possesses, or that are located in any place under its jurisdiction or control, as well as any CW it abandoned on the territory of another state. The CWC was opened for signature on 13 January 1993, and entered into force on 29 April 1997. For additional information, see the CWC.
Chemical Weapon (CW)
The CW: The Organization for the Prohibition of Chemical Weapons defines a chemical weapon as any of the following: 1) a toxic chemical or its precursors; 2) a munition specifically designed to deliver a toxic chemical; or 3) any equipment specifically designed for use with toxic chemicals or munitions. Toxic chemical agents are gaseous, liquid, or solid chemical substances that use their toxic properties to cause death or severe harm to humans, animals, and/or plants. Chemical weapons include blister, nerve, choking, and blood agents, as well as non-lethal incapacitating agents and riot-control agents. Historically, chemical weapons have been the most widely used and widely proliferated weapon of mass destruction.
Organization for the Prohibition of Chemical Weapons (OPCW)
The OPCW: Based in The Hague, the Netherlands, the OPCW is responsible for implementing the Chemical Weapons Convention (CWC). All countries ratifying the CWC become state parties to the CWC, and make up the membership of the OPCW. The OPCW meets annually, and in special sessions when necessary. For additional information, see the OPCW.
Missile Technology Control Regime (MTCR)
The MTCR: An informal arrangement established in April 1987 by an association of supplier states concerned about the proliferation of missile equipment and technology relevant to missiles that are capable of carrying a payload over 500 kilograms over a 300-kilometer range. Though originally intended to restrict the proliferation of nuclear-capable missiles, the regime has been expanded to restrict the spread of unmanned aerial vehicles. For additional information, see the MTCR.
Space Launch Vehicle (SLV)
A rocket used to carry a payload, such as a satellite, from Earth into outer space. SLVs are of proliferation concern because their development requires a sophisticated understanding of many of the same technologies used in the development of long-range ballistic missiles (e.g., propulsion, guidance and control, staging, and structures). Some states (e.g., Iran), may have developed SLV programs in order to augment their ballistic missile capabilities.
Theater High Altitude Air Defense (THAAD)
THAAD: The U.S. Army's air defense program designed to provide extended defense, and to engage an incoming missile at ranges of up to several hundred kilometers. THAAD deploys a hit-to-kill interceptor equipped with an infrared seeker. The interception is intended to occur outside the earth's atmosphere, or high in the atmosphere.
Intercontinental ballistic missile (ICBM)
Intercontinental ballistic missile (ICBM): A ballistic missile with a range greater than 5,500 km. See entry for ballistic missile.


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