Overview Last updated: December, 2015
South Korea has maintained a bilateral security alliance with the United States since the Korean War (1950-1953).  Seoul abandoned its nuclear weapons program in the 1970s, but has the latent technical capacity to produce nuclear weapons. 
South Korea is a signatory to several nonproliferation treaties and has adopted a policy aimed at maintaining a "nuclear-free Korean peninsula."  Seoul is a party to the Biological and Toxin Weapons Convention (BTWC).  Although Seoul has never admitted to this in a public forum, South Korea is understood — based on various media reports and comments by relevant experts — to have declared its possession of chemical weapons as part of its obligation under the Chemical Weapons Convention (CWC); this stockpile was fully destroyed as of 2008 under the supervision of the Organization for the Prohibition of Chemical Weapons (OPCW).  In October 2012 South Korea and the U.S. agreed to extend the range and payload capacity of South Korea’s missiles up to 800 km with 500 kg payload. 
South Korea first became interested in nuclear technology in the 1950s, but did not begin construction of its first power reactor until 1970.  South Korea currently has 24 civilian nuclear power reactors in use and four under construction.  Changes in the international security environment influenced South Korea's decision to begin a nuclear weapons program in the early 1970s. Under significant pressure from the United States, however, Seoul abandoned this program and signed the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in April 1975 before it had produced any fissile material.  Seoul is a state party to the Comprehensive Nuclear Test Ban Treaty (CTBT), and a member of the Nuclear Suppliers Group and the Zangger Committee. 
In November 1991, President Roh Tae-woo declared that South Korea would not "manufacture, possess, store, deploy, or use nuclear weapons."  Two months later, North and South Korea signed the Joint Declaration on the Denuclearization of the Korean Peninsula. In this agreement, Seoul and Pyongyang agreed not "to test, manufacture, produce, receive, possess, store, deploy or use nuclear weapons," and not to "possess nuclear reprocessing and uranium enrichment facilities."  However, both sides failed to implement the agreement's provisions relating to a bilateral inspection regime.  Although North Korea has clearly violated the Joint Declaration, particularly in light of its three nuclear weapons tests (in 2006, 2009, and 2013), South Korea never officially renounced its obligations under the declaration, and has called on the North to abide by the agreement.  Seoul has been a participant in the Six-Party Talks since their inception in 2003, which are aimed at ending the nuclear crisis on the Korean Peninsula. 
South Korea was bound by a 1974 bilateral pact with the United States banning the reprocessing of spent nuclear fuel. A technology known as pyroprocessing was proposed by South Korea as a viable option; however, the U.S. was reluctant to accept it stating that pyroprocessing is a form of reprocessing.  The pact was extended two more years, set to expire in 2016, after both sides failed to agree to new terms upon the passing of the original deadline in 2014.  In April 2015, South Korea and the U.S. reached a deal to revise the pact, lifted the ban on the reprocessing of spent nuclear fuel as well as uranium enrichment, and reaffirmed the research on pyroprocessing technology; the South Korean Cabinet approved the agreement in June. 
The issue of possible redeployment of U.S. tactical nuclear weapons to South Korea has been debated since 2010. Although both Washington and Seoul deny the possibility — asserting that no such plans are under consideration or necessary for South Korea’s defense — hardliner politicians in South Korea such as Representative Chung Mong-joon of the ruling Saenuri party (formerly Grand National Party) welcomed the prospect.  In February 2013, immediately following the 2013 North Korean nuclear test, the Asan Institute for Policy Studies (founded by Chung) conducted a survey of 1,000 South Koreans, which showed about 66 percent support the idea that South Korea should develop their own nuclear weapons to counteract North Korea. 
In March 2012, South Korea hosted the second Nuclear Security Summit. The Seoul Communique, which emphasizes nuclear security and encourages all State parties to minimize their highly enriched uranium (HEU), was adopted unanimously.  As of the 2014 summit, South Korea reported that it was cooperating with Germany, the U.S., France, and Belgium to develop a technology which converts HEU in their research reactors to low enriched uranium (LEU). 
South Korea ratified the Biological and Toxin Weapons Convention (BTWC) in June 1987 and joined the Australia Group in October 1995.  While South Korea possesses a well-developed pharmaceutical and biotech infrastructure, there is no evidence that Seoul has an offensive biological weapons (BW) program.  In its 2006 Defense White Paper, South Korea stated a need for defensive BW research and development, including the development of vaccines against anthrax and smallpox, however this research has not been cited since the 2010 Ministry of National Defense White Paper. 
South Korea ratified the Chemical Weapons Convention (CWC) in April 1997.  Upon its ratification of the treaty, South Korea — according to many reliable sources — 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). Despite the fact that Seoul is widely understood to have declared its CW stockpile and facilities, neither the OPCW nor Seoul has publicly acknowledged this declaration. The South Korean government has maintained a high level of secrecy regarding its previous chemical weapons activities, making no public announcements and 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 (충청북도 영동군). 
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 completed the destruction of its entire chemical weapons stockpile in July 2008, becoming the second CWC member to do. 
In the wake of the shelling of Yeonpyeong Island in November 2010, the ROK 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 the North.  Additionally, the U.S. chemical warfare battalion, which left South Korea in 2004, was redeployed to the Korean peninsula in 2013. 
South Korea began developing missiles in the early 1970s. In December 1971, South Korean President Park Chung-hee (박정희) issued a directive to reverse-engineer the U.S. Nike Hercules air defense missile, a system that can also be used as a surface-to-surface system. Following several failures, South Korea's first successful test of its own version, the Baekgom (백곰) system, was conducted in September 1978. In 1979, South Korea entered into a bilateral agreement with the United States that limited South Korean ballistic missiles to a range of 180 km with a 500 kg payload. The Baekgom program was slashed in December 1982, but was restored in late 1983. South Korea subsequently developed an improved version of the Baekgom, called the Hyonmu (현무).  Currently South Korea deploys a series of short-range ballistic missiles and two types of cruise missiles. South Korea joined the Missile Technology Control Regime (MTCR) in March 2001; membership in the organization limits the missile-range and payload to 300 km and 500 kg, respectively, and supersedes the missile-range agreement concluded earlier with Washington.  In January 2002, South Korea announced procurement of the 300 km-range Army Tactical Missile System (ATACMS) from the United States, purchasing 220 ATACMS by 2004. 
Since 2011, South Korea sought to extend the range of its missiles by up to 800-1000 km, arguing that North Korea is in possession of the 1,300 km range Nodong; however, the U.S. blocked an extension citing concern about heightening tension on the Korean peninsula. On 7 October 2012 both countries agreed to extend South Korea’s missile range up to 800 km with 500 kg payload. In addition, a ‘trade-off’ provision was included, which allows South Korea to increase the payloads proportionally to a decrease in the range of its short-range missiles. Both countries also agreed to increase the payload capacity of unmanned aerial vehicles (UAVs) from 500 kg to 2500 kg. 
In the 1990s, Seoul began development of its own space program, including the development of a space-launch vehicle (SLV). After numerous delays, South Korea launched the two-stage KSLV-1 rocket on 25 August 2009. The launch was intended to place an earth and atmospheric monitoring satellite—the Science and Technology Satellite-2 (STSTAT-2)—into orbit. The satellite reached an altitude of about 390 km, but could not maintain an orbit; it was destroyed during re-entry into the Earth's atmosphere.  In a 2010 launch, the rocket exploded 137 seconds after takeoff.  Seoul ultimately achieved a successful orbit in January 2013.  The success of this launch raises concerns that South Korea has sufficient technology for a long-range ballistic missile system that could deliver WMD payloads. 
In March 2014, South Korea successfully tested a new ballistic missile with a range of 500 km, which is capable of striking the North. 
In April 2015, the Ministry of National Defense submitted its budget for the 2016-2020 period, requesting KRW 232.5 trillion to improve missile capabilities and ensure deterrence against the North.  In June 2015, South Korea tested a longer-range ballistic missile capable of striking all parts of North Korea; Seoul reportedly plans to deploy the missile by the end of 2015. 
 The White House, “Joint-Fact Sheet: The United States-Republic of Korea Alliance. A Global Partnership,” 25 April 2014, www.whitehouse.gov.
 Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, 9 November 2004, www.nonproliferation.org; Graham Jenkins, “Failure to Ignite: Sarah Weiner ed., The Absence of Cascading Nuclear Proliferation,” Nuclear Scholars Initiative, ed. (New York: CSIS, 2014).
 “Park, Xi Vow Denuclearization of Korean Peninsula,” Yonhap, 3 July 2014, http://english.yonhapnews.co.kr.
 United Nations Office for Disarmament Affairs, "Status of Multilateral Arms Regulation and Disarmament Agreements," www.un.org; United Nations Office for Disarmament Affiars, "Disarmament Treaties Database: Biological Weapons Convention," http://disarmament.un.org.
 Chris Schneidmiller, "South Korea Completes Chemical Weapons Disposal," Global Security Newswire, 17 October 2008, www.nti.org.
 Cheong Wa Dae, "한·미 미사일지침 개정 결과 관련 브리핑 [Briefing on Revision of Korean-American Missile Guidelines," Office of the President of the Republic of Korea, 7 October 2012, www.president.go.kr.
 Ha Yeong-seon, 한반도의 핵무기와 세계질서 [Nuclear Weapons on the Korean Peninsula and World Order] (Seoul: Nanam, 1991).
 International Atomic Energy Agency, "Korea, Republic of," Power Reactor Information System Database, December 2014, http://pris.iaea.org.
 Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, 9 November 2004, www.nonproliferation.org.
 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.
 Roh Tae Woo, "President Roh Tae Woo's Declaration of Non-Nuclear Korean Peninsula Peace Initiatives," 8 November 1991, http://fas.org.
 "Korean Denuclearization Agreement," 20 January 1992, via: www2.law.columbia.edu.
 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 July 23-24, 2001 Workshop, p.154, http://isis-online.org.
 "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.
 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.
 Kim Kyung-tae, "핵연료 재처리 가능할까? [Will South Korea be Allowed to Reprocess Spent Nuclear Fuel?]" Hwan-kyung Ilbo, 25 November 2011, www.hkbs.co.kr; "S. Korea, US Resume Talks on Nuclear Energy," Agence France-Presse, 5 December 2011; Grace Oh, "S. Korea, US resume talks on key nuke energy pact," Yonhap, 7 January 2014, http://english.yonhapnews.co.kr.
 Hou Qiang, ed., "S. Korea, U.S. to Extend Nuclear Pact for Another 2 Years,” Xinhua English News, 24 April 2013, http://news.xinhuanet.com.
 Jack Kim, “South Korea, U.S. Reach Deal to Revise Civil Nuclear Pact,” Reuters, 22 April 2015, www.reuters.com; “S. Korean Cabinet OKs Nuclear Deal with U.S.,” Yonhap News Agency, 8 June 2015, http://english.yonhapnews.co.kr.
 Duyeon Kim, "Tactical Nuclear Weapons & Korea: a Temporary or Perennial Debate?" The Center for Arms Control and Non-Proliferation, June 2011, http://armscontrolcenter.org; "Tactical Nukes Only Way to Deter N.K Nuclear Ambitions," The Korea Herald, 31 March 2013, www.koreaherald.com; "S. Korean PM Against Redeploying US Tactical Nuclear Weapons," RIA Novosti, 25 April 2013, http://en.ria.rul.
 The survey was conducted in February 2013, among 1,000 South Koreans. They were interviewed via RDD for mobile and landline phones. The margin of error is ± 3.1% at the 95% confidence level. "The Fallout: South Korea Public Opinion Following North Korea’s Third Nuclear Test," The Asan Institute for Policy Studies, February 2011, http://en.asaninst.org.
 Choi He-suk, "Korea Teams Up with U.S. Belgium, France on HEU," The Korea Herald, 27 March 2012, http://khnews.kheraldm.com.
 Republic of Korea, "Nuclear Security Summit 2014: National Progress Report," 5 March 2014, www.nss2014.com.
 United Nations Office for Disarmament Affairs, "Status of Multilateral Arms Regulation and Disarmament Agreements," www.un.org; "Australia Group Participants," www.australiagroup.net.
 Republic of Korea Ministry of National Defense, "2012 Defense White Paper," December 2012, www.mnd.go.kr.
 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 Defense, "2012 Defense White Paper," December 2012, www.mnd.go.kr.
 Organisation for the Prohibition of Chemical Weapons, "Member State – Republic of Korea," www.opcw.org.
 "Report: Korean Army Built Factory to Destroy Chemical Weapons," Deutsche Presse-Agentur, 9 May 2000.
 Chris Schneidmiller, "South Korea Completes Chemical Weapons Disposal," Global Security Newswire, 17 October 2008, www.nti.org.
 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.
 "U.S. Chemical Warfare Battalion to Return to Korea," 8 October 2012, Chosun Ilbo, http://english.chosun.com; Jon Rabiroff, "Chemical Weapon Unit Back in South Korea: Timing Coincidental," 4 April 2013, Stars and Stripes, www.stripes.com.
 Joseph S. Bermudez Jr., "A History of Ballistic Missile Development in the DPRK," CNS Occasional Paper, 9 February 2000, www.nonproliferation.org.
 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.
 "S. Korea Deploys Precisions-guided Missiles Targeting Pyongyang," Yonhap, 17 June 2011, http://english.yonhapnews.co.kr.
 Cheong Wa Dae, "한·미 미사일지침 개정 결과 관련 브리핑," Office of the President of the Republic of Korea, 7 October 2012, www.president.go.kr.
 Kim Tong-hyung, "Satellite Fails to Enter Orbit," Korea Times, 25 August 2009, www.koreatimes.co.kr.
 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.
 Wa Zhou and Guangjin Cheng, "Republic of Korea Hopes for Third Time Lucky on Rocket Launch," China Daily, 30 January 2013, http://usa.chinadaily.com.cn.
 Jack Kim, “South Korea Extending Ballistic Missile Range to Counter North’s Threat,” Reuters, 4 April 2014, www.reuters.com.
 Oh Seok-min, “S. Korea to Raise Defense Spending by 2020,” Yonhap News Agency, 19 April 2015, http://english.yonhapnews.co.kr.
 “S. Korea Test-fires Longer-range Ballistic Missile,” Yonhap News Agency, 3 June 2015, http://english.yonhapnews.co.kr.
This material is produced independently for NTI by the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2015.
Get the Facts on South Korea
- Operates 23 nuclear power reactors which provide 35% of its electricity
- Completed destruction of its chemical weapons stockpile in July 2008
- Owns a well-developed biotechnology infrastructure, but no evidence suggests the pursuit of a biological weapons program