Last Updated: August, 2017
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.  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 nuclear weapons tests (in 2006, 2009, 2013, and 2016), South Korea never officially renounced its obligations under the declaration, and has called on the North to abide by the agreement.  Seoul was a participant in the Six-Party Talks, aimed at ending the nuclear crisis on the Korean Peninsula, until North Korea pulled out in 2009 after disagreements with the UN Security Council. 
South Korea currently has 24 civilian nuclear power reactors in use and three under construction.  Despite the country’s large, well-developed civil nuclear sector, in June 2017, President Moon Jae-in announced plans to phase out nuclear power. This will include halting plans for new reactors and not extending the lifespans of current reactors. 
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. 
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, and successfully tested its first missile system Baekgom in September 1978. 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.  In response to North Korea’s Unha-3 rocket launch in 2012, Seoul came to an agreement with Washington to allow South Korea to extend the range of its ballistic and cruise missiles to 800 kilometers, far enough to strike targets anywhere in North Korea. 
In the 1990s, Seoul began development of its own space program, including a space-launch vehicle (SLV). After numerous delays, South Korea launched the two-stage KSLV-1 rocket on August 25, 2009. The launch was unsuccessful, as was a 2010 launch.  Seoul ultimately achieved a successful space launch and placed a satellite into orbit in January 2013. 
In the wake of North Korea’s January 6, 2016 nuclear test and February 7, 2016 liquid-fueled Unha rocket –boosted satellite launch, South Korea made efforts in concert with the U.S. to improve its ballistic missile defense.  In early 2017, the United States deployed two Terminal High Altitude Aerial Defense (THAAD) systems in South Korea.  Four more THAAD systems are planned, but have been halted due to environmental concerns. After North Korean ICBM tests in 2017, President Moon Jae-in called for discussion of increasing the number of missile defense units in South Korea.  In addition to the THAAD systems, the United States has Patriot and Aegis missile defense systems deployed in the region. 
 The White House, "Joint-Fact Sheet: The United States-Republic of Korea Alliance. A Global Partnership," April 25, 2014, www.whitehouse.gov.
 Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, November 9, 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, July 3, 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 Affairs, "Disarmament Treaties Database: Biological Weapons Convention," http://disarmament.un.org.
 Chris Schneidmiller, "South Korea Completes Chemical Weapons Disposal," Global Security Newswire, October 17, 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, October 7, 2012, www.president.go.kr.
 Ha Yeong-seon, 한반도의 핵무기와 세계질서 [Nuclear Weapons on the Korean Peninsula and World Order] (Seoul: Nanam, 1991).
 Daniel A. Pinkston, "South Korea's Nuclear Experiments," CNS Research Story, November 9, 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, January 13, 2010, www.zanggercommittee.org.
 Roh Tae Woo, "President Roh Tae Woo's Declaration of Non-Nuclear Korean Peninsula Peace Initiatives," November 8, 1991, www.fas.org.
 "Korean Denuclearization Agreement," January 20, 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, www.isis-online.org.
 "North Korea's Nuclear Tests," BBC, February 12, 2013, www.bbc.com; "Text of the Joint Statement," The New York Times, September 19, 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, June 16, 2014, www.koreaherald.com; Mark Landler, “North Korea Says It Will Halt Talks and Restart Its Nuclear Program,” The New York Times, April 14, 2009, nytimes.com.
 International Atomic Energy Agency, "Korea, Republic of," Power Reactor Information System Database, July 2017, http://pris.iaea.org.
 Jane Chung, “South Korea's President Moon says plans to exit nuclear power,” Reuters, June 18, 2017, reuters.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, May 9, 2000.
 Chris Schneidmiller, "South Korea Completes Chemical Weapons Disposal," Global Security Newswire, October 17, 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, October 4, 2011, http://news.donga.com.
 "U.S. Chemical Warfare Battalion to Return to Korea," Chosun Ilbo, October 8, 2012, http://english.chosun.com; Jon Rabiroff, "Chemical Weapon Unit Back in South Korea: Timing Coincidental," Stars and Stripes, April 4, 2013, www.stripes.com.
 Lee Min-jung, "탄도미사일 사거리 연장되나 [Will the Missile Range be Extended for South Korea?]" EDAILY, June 13, 2012, www.edaily.co.kr; Missile Technology Control Regime, "MTCR Partners," www.mtcr.info.
 "Choe Sang-Hun, “U.S. Agrees to Let South Korea Extend Range of Ballistic Missiles,” The New York Times, October 7, 2012, www.nytimes.com.
 Tong-hyung Kim, "Naro Rocket Blows Up in Midair," The Korea Times, June 10, 2010, www.koreatimes.co.kr.
 Jung-yoon Choi and Barbara Demick, "South Korea Launches Satellite into Orbit," The Los Angeles Times, January 30, 2013, www.latimes.com.
 Michael Elleman, "North Korea Launches Another Large Rocket: Consequences and Options," 38 North, February 10, 2016.
 Alex Johnson, Stella Kim, Courtney Kube, “U.S. Begins Shipping Controversial Anti-Missile System to South Korea,” NBC News, March 7, 2017, nbcnews.com.
 Jack Kim, “South Korea's president wants to talk to the US about more missile defenses after North Korea's ICBM test,” Business Insider, July 28, 2017, businessinsider.com.
 Brad Lendon, “How would missile defense systems work against North Korea?” CNN, March 7, 2017, cnn.com.
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