1. How many nuclear tests have been conducted since the CTBT was negotiated?
9 tests, with 16 detonations, have been conducted by 3 different countries since 1996:
- India conducted 5 underground test detonations as part of two test series on May 11 and May 13, 1998, but subsequently declared a moratorium on nuclear testing.  India claimed to have tested a fission device with a 12 kiloton yield, three sub-kiloton devices, and a thermonuclear device with a 43 kiloton yield.  Many analysts believe the thermonuclear test failed and note that the advertised kiloton yields are significantly higher than the cumulative yield estimates measured using the CTBTO’s seismic monitoring stations. 
- Pakistan conducted 6 underground test detonations as part of two test series. Five simultaneous test detonations were conducted on May 28, and one detonation on May 30, 1998. According to the Pakistani declarations, the first series of tests consisted of three sub-kiloton, low-yield devices, one fission device with a yield of 12 kilotons, and one boosted fission device with a 25-36 kiloton yield. The single test carried out on May 30th was a fission device with a 12 kiloton yield, although all yield announcements have been challenged as possibly lower according to seismic data recorded by the CTBTO’s monitoring stations.  Pakistan also declared a moratorium on nuclear testing following these tests.
- North Korea has conducted 5 underground tests, once each in 2006, 2009 and 2013, and two in 2016.  North Korea has not declared a moratorium on testing, and regularly threatens to test nuclear weapons again.
2. Why did India and Pakistan test nuclear weapons in 1998?
India first tested a nuclear device in 1974, although it labelled the event as a “peaceful nuclear explosion.” India’s decision to test again in 1998 was controversial because it was shortly after the negotiation of the CTBT. Factors that influenced India’s decision to conduct a nuclear test included:
- Domestic political shifts: The Bharatiya Janata Party (BJP) won the February 1998 Indian general election after campaigning on a pro-nuclear weapons platform.
- Regional Tensions: The election of a more hardline government in India and Pakistan’s April 1998 Ghauri-1 medium-range ballistic missile test increased tensions between the two long-time rivals.
- International Diplomacy: Many Indian policymakers viewed developments in the international nonproliferation regime, particularly the 1995 indefinite extension of the Nuclear Nonproliferation Treaty (NPT) and negotiation of the Comprehensive Nuclear Test-Ban Treaty (CTBT), as particularly disadvantageous for India’s strategic position. 
Pakistan tested just two weeks following India’s tests:
- Although it might have ultimately decided to test regardless of whether India tested, Pakistan’s decision to test in May 1998 was primarily a reaction to the fact that its primary adversary, India, had just done so. 
3. Why does the international community consider NK’s nuclear testing program a threat?
- North Korea is outside of all nuclear nonproliferation treaties and regimes. It announced its intent to withdraw from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1994, and did so in 2003.  North Korea has not signed or ratified the CTBT. 
- North Korea possesses a complete indigenous nuclear fuel cycle, from mining to reactor operations and weapons production, including uranium enrichment and plutonium production facilities.  None of these activities are under international safeguards.
- Beginning in the 1980s, North Korea began pursuing a ballistic missile program. It is known to have short and mid-range ballistic missiles, and is pursuing long-range ballistic missile capabilities.  In 2013, the U.S. Defense Intelligence Agency assessed with moderate confidence that North Korea possessed “nuclear weapons capable of delivery by ballistic missiles,” but added that the reliability of these weapons would be low. 
- North Korea has threatened to use its nuclear weapons on several occasions. In March 2013, North Korea threatened to strike the United States with “lighter and smaller nukes.”  North Korea has threatened South Korea several times with a nuclear attack, including by threatening the “final destruction” of the country. 
- North Korea has violated previously-made commitments to nonproliferation through its nuclear testing. These include the Agreed Framework of 1994; North Korea’s Comprehensive Safeguards Agreement with the International Atomic Energy Agency (IAEA); and numerous UNSC Resolutions.  Additionally, many states argue that North Korea did not follow the appropriate procedures to withdraw from the NPT, invalidating its withdrawal and placing North Korea in violation of its NPT obligations. 
- North Korea is greatly increasing its military capabilities through routine nuclear tests.
Explore the below timeline to learn more about how North Korea has used nuclear tests to advance the sophistication and capabilities of its nuclear weapons program.
4. How has the international community responded to North Korea’s testing activities?
International condemnation was nearly unanimous following each of North Korea’s nuclear tests. Although the CTBT has not yet entered into force, there is widespread international consensus on the importance of an indefinite global test moratorium.
- The United Nations Security Council has responded to each North Korean nuclear test with unilateral condemnation and increasingly stringent economic sanctions.
|October 2006||UNSCR 1718||
|June 2009||UNSCR 1874||
|March 2013||UNSCR 2094||
|March 2016||UNSCR 2270||
|November 2016||UNSCR 2321||
- Numerous countries issued statements of condemnation, including the five permanent members of the UN Security Council (U.S., U.K., Russia, China, and France), South Korea, and Japan. Speaking at the United Nations, for example, Japanese Prime Minister Shinzo Abe stated that North Korea had “manifested itself… as an open threat to peace.” 
- Despite being North Korea’s traditional ally and largest trading partner, China helped draft the 2013 UNSC sanctions with the United States, signaling its growing frustration with North Korea’s behavior.  In November 2016, China also agreed to a substantial cut in its imports of North Korean coal, an important economic lifeline for the North Korean regime. However, China has also accused the U.S. and South Korea of “gravely under[mining] the regional strategic balance” and thus running “counter to the efforts to safeguard peace and stability” on the Korean peninsula through the two allies’ planned deployment of the Terminal High Altitude Area Defense anti-ballistic missile system in South Korea. 
5. What has the international community learned about NK’s nuclear program from its tests, and how does what was learned support CTBT entry-into-force?
- Test data suggests North Korea has been trying to develop a compact, lightweight nuclear warhead, which could be suitable for delivery by ballistic missiles. Pyongyang claimed in 2008 that the 2006 test used only 2kg of plutonium. 
- Satellite imagery of facilities at the Punggye-ri test site shows signs of expansion, including new tunnels and buildings. 
A 3D model of North Korea’s nuclear test site, by the Center for Nonproliferation Studies, suggests many more tests may be planned.
Click the play button to learn more about North Korea’s nuclear test site and the Mount Mantap tunnel complex with this interactive 3D model – Or explore the model in VR with Google Cardboard (or other VR headset) by clicking the VR headset icon in the bottom right corner. Don’t forget to view the model in HD by adjusting the quality setting in the gear icon. To learn how to use VR please click on this link for a pdf explanation.
For more information, see Jeffrey Lewis’s article, “North Korea’s Nuclear Year In Review—And What’s Next.”
- Both the Preparatory Commission’s International Monitoring System (IMS) and states’ national technical means (NTMs) successfully detected all five of North Korea’s nuclear tests. This supports the assertion that the IMS is capable of detecting covert nuclear tests with a yield above a kiloton. 
 Federation of American Scientists, India, Last modified November 8, 2002. http://fas.org/nuke/guide/india/nuke/; “India and Pakistan Statements to the United Nations General Assembly, September 1998,” The Acronym Institute for Disarmament Diplomacy. http://www.acronym.org.uk/spsep98.htm
 George Perkovich, India’s Nuclear Bomb: The Impact on Global Proliferation (Berkeley: University of California Press, 1999), p. 416, 419.
 George Perkovich, India’s Nuclear Bomb: The Impact on Global Proliferation (Berkeley: University of California Press, 1999), p. 416, 419.
 Jeffrey Lewis, “India’s H Bomb Revisited,” Arms Control Wonk, August 27, 2009, http://www.armscontrolwonk.com/archive/202445/indias-h-bomb-revisited/
 Gregory van der Vink, Jeffrey Park, Richard Allen, Terry Wallace and Christel Hennet, “False Accusations, Undetected Tests and Implications for the CTB Treaty,” Arms Control Today, May 1, 1998. https://www.armscontrol.org/act/1998_05/vimy98
 “Pakistan Nuclear Weapons,” Federation of American Scientists, Accessed December 22, 2015. http://fas.org/nuke/guide/pakistan/nuke/; and http://www.acronym.org.uk/spsep98.htm
 “North Korea: Nuclear” Nuclear Threat Initiative, Last modified September 2016. http://www.nti.org/country-profiles/north-korea/nuclear/
 George Perkovich, India’s Nuclear Bomb: The Impact on Global Proliferation (Berkeley: University of California Press, 1999), p. 358-359, 379.
 Sublette, Carey, “1998: The Year of Testing,” Pakistan’s Nuclear Weapons, Nuclear Weapon Archive, Last modified September 10, 2001. http://nuclearweaponarchive.org/Pakistan/PakTests.html; Khan, Feroz Hassan, Eating Grass: The Making of the Pakistani Bomb, Stanford: Stanford UP, 2012: pp 270-279.
 Davenport, Kelsey, “Chronology of US- North Korea Nuclear and Missile Diplomacy,” Arms Control Association, Last modified October 2016. https://www.armscontrol.org/factsheets/dprkchron
 CTBTO, “Status of Signature and Ratification,” Preparatory Commission for the Comprehensive Test Ban Treaty, Last modified June 2015. https://www.ctbto.org/the-treaty/status-of-signature-and-ratification/
 Lewis, Jeffrey, “Recent Imagery Suggests Increased Uranium Production in North Korea, Probably for Expanding Nuclear Weapons Stockpile and Reactor Fuel,” 38 North, US-Korea Institute at SAIS, Last modified August 12, 2015. http://38north.org/2015/08/jlewis081215/
 “North Korea’s Missile Programme,” BBC, Last modified June 17, 2014. http://www.bbc.com/news/world-asia-17399847
 U.S. Congress, House Committee on Armed Services, Hearing on the Defense Authorization Act for Fiscal Year 2014 and Previously Authorized Programs, 113th Cong., 1st Session, April 11, 2013: pp 51-52.
 Sang-Hun, Choe, “North Korea Threatens to Attack U.S. with ‘Lighter and Smaller Nukes.'” New York Times, Last modified March 5, 2013. http://www.nytimes.com/2013/03/06/world/asia/north-korea-threatens-to-attack-us-with-lighter-and-smaller-nukes.html.
 Sinha, Shreeya, and Susan Beachy, “Timeline on North Korea’s Nuclear Program,” New York Times, Last modified November 20, 2014. http://www.nytimes.com/interactive/2014/11/20/world/asia/northkorea-timeline.html#/#time238_7118; Browne, Ryan and Barbara Starr, “North Korea threatens nuclear strike amid US-South Korea drill,” CNN, Last modified August 22, 2016.
 Davenport, Kelsey, “Chronology of US- North Korea Nuclear and Missile Diplomacy,” Arms Control Association, Last modified May 2015. https://www.armscontrol.org/factsheets/dprkchron
 Bunn, George, and John B. Rhinelander, “NPT Withdrawal: Time for the Security Council to Step In,” Arms Control Association, Accessed November 20, 2015. https://www.armscontrol.org/act/2005_05/Bunn_Rhinelander
 United Nations Security Council resolution 1718, S/RES/1718 (October 14, 2006). https://www.globalpolicy.org/images/pdfs/1014reso1718.pdf
 UN Security Council, “Resolution 1874 (2009) Strengthens Arms Embargo, Calls for Inspection of Cargo, Vessels If States Have ‘Reasonable Grounds’ to Believe Contain Prohibited Items,” United Nations Meetings Coverage and Press Releases, United Nations, Last modified June 12, 2009. http://www.un.org/press/en/2009/sc9679.doc.htm
 UNSC, “Security Council Strengthens Sanctions on Democratic People’s Republic of Korea, in Response to 12 February Nuclear Test,” United Nations, Last modified March 7, 2013. http://www.un.org/press/en/2013/sc10934.doc.htm
 United Nations, Department of Public Information, “Security Council Imposes Fresh Sanctions on Democratic People’s Republic of Korea, Unanimously Adopting Resolution 2270,” SC/12267, Last modified March 2, 2016. http://www.un.org/press/en/2016/sc12267.doc.htm
 United Nations, Department of Public Information, “Security Council Strengthens Sanctions on Democratic Republic of Korea, Unanimously Adopting Resolution 2321 (2016),” SC/12603, Last modified November 30, 2016. https://www.un.org/press/en/2016/sc12603.doc.htm
 United Nations, Department of Public Information, “Japanese Prime Minister Abe calls for resolute UN action against DPR Korea’s nuclear threat,” September 21, 2016. http://www.un.org/apps/news/story.asp?NewsID=55010#.WAVa7k2YZHg
 “July 11, 1961: “China-DPRK Treaty of Friendship, Cooperation and Mutual Assistance” was signed in Beijing,” News of the Communist Party of China. http://cpc.people.com.cn/GB/4162/64165/67447/67825/4577963.html
 United Nations COMTRADE Database, Periods: 2015, Reporters: All, Partners: Dem. People’s Rep. of Korea, Trade Flows: All, https://comtrade.un.org/data/ (accessed December 8, 2016).
 Gladstone, Rick, and David Sanger, “New Sanctions on North Korea Pass in Unified UN Vote,” New York Times, March 7, 2013.
 Ministry of Foreign Affairs of the People’s Republic of China, “Foreign Ministry Spokesperson Geng Shuang’s Regular Press Conference on November 16, 2016,” November 16, 2016. http://www.fmprc.gov.cn/mfa_eng/xwfw_665399/s2510_665401/t1415936.shtml
 Wertz, Daniel, and Matthew McGrath, “North Korea’s Nuclear Weapons Program,” The National Committee on North Korea, Last modified September 2015. http://www.ncnk.org/resources/publications/DPRK-Nuclear-Weapons-Issue-Brief
 Liu, Jack, “North Korea’s Punggye-ri Nuclear Test Site: Activity Spotted at All Three Portals,” 38 North, US-Korea Institute at SAIS, Last modified October 6, 2016. http://38north.org/2016/10/punggye100616/
 “Report of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization prepared for the 2015 Review Conference of the Parties to the Treaty on the Non-Proliferation of Nuclear Weapons,” Report submitted by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, NPT/CONF.2015/19, March 27, 2015.
 Kang, Jungmin, and Peter Hayes, “Technical Analysis of the DPRK Nuclear Test,” Nautilus Institute for Security and Sustainability, October 21, 2006. http://nautilus.org/napsnet/napsnet-special-reports/technical-analysis-of-the-dprk-nuclear-test/
 Wertz, Daniel, and Matthew McGrath, “North Korea’s Nuclear Weapons Program,” The National Committee on North Korea, January 2016. http://www.ncnk.org/resources/publications/DPRK-Nuclear-Weapons-Issue-Brief
 “North Korea’s 2016 Nuclear Test Location and Yield: Seismic Results from USTC,” University of Science and Technology of China, January 6, 2016. http://seis.ustc.edu.cn/en/201609/t20160909_253324.html
 Wertz, Daniel, and Matthew McGrath, “North Korea’s Nuclear Weapons Program,” The National Committee on North Korea, January 2016.
 Kim, Jack, “South Korea says North’s nuclear capability ‘speeding up’, calls for action,” Reuters, September 11, 2016. http://uk.reuters.com/article/uk-northkorea-nuclear-idUKKCN11F02D
 Lewis, Jeffrey, “North Korea’s Nuclear Program Is Way More Sophisticated Than You Think,” Foreign Policy, September 9, 2016. http://foreignpolicy.com/2016/09/09/north-koreas-nuclear-program-is-way-more-sophisticated-and-dangerous-than-you-think/
Header Image: The Chaghi Monument commemorates Pakistan’s nuclear tests in 1998. Source: WikiMedia Commons, Khalid Mahmood.