The NTI Submarine Proliferation Resource Collection details the submarine capabilities and import/export behavior of several representative countries around the world. The collection focuses on technological improvements to global submarine fleets, such as the spread of nuclear propulsion and Air Independent Propulsion (AIP) technologies, which increase the capability of submarines to deliver weapons of mass destruction (WMD). Additionally, the collection tracks conventional submarine proliferation in potential global flashpoints, particularly the Middle East, South Asia, and Southeast Asia.
Submarine proliferation impacts both regional stability and the ability of states to deliver WMD. Since the end of the Cold War, the total number of active submarines in the world has fallen, largely as a result of large-scale decommissioning of former Soviet vessels.  However, the number of countries operating submarines has increased, due largely to ongoing regional tensions in the Middle East, South Asia, and East Asia. Countries that seek to acquire submarines can rely on a competitive global export market, which is only lightly regulated by international export controls.
An Evolving Export Market
Although the number of states acquiring submarines has grown in recent decades, the group of countries exporting submarines has remained relatively small. Today, France, Germany and Russia are the three most active exporters of conventional submarines. France's Direction des Constructions Navales Services (DCNS) and Germany's Howaldtswerke Deutsche Werft (HDW) are the two principal submarine producers in their respective countries.  Between them, they have exported to approximately 21 navies.  Meanwhile, Russia has a number of design and construction enterprises, and has exported conventional boats to some 14 navies around the world. Recipients of Russian diesel-powered submarines include China, Iran, India, and Vietnam. China has concluded submarine deals with countries such as Pakistan, Thailand, and Bangladesh, and appears to have greater aspirations in the export market.  South Korea has also entered the submarine export market, delivering its first Daewoo-built attack submarines to the Indonesian Navy in 2016. 
Competition among exporters for lucrative construction contracts can be fierce, and this has often led to producers offering technology transfer to secure deals. One example is France's production technology transfer to Brazil as part of its 2008 sale of Scorpène-class vessels.  Technology transfers of this kind will likely result in the proliferation of submarine producers as recipients become capable of constructing their own submarines.
Air Independent Propulsion (AIP) technology provides diesel-powered submarines with greater submerged endurance (several weeks as opposed to several days), thereby enhancing survivability.  This is achieved through the use of liquid or compressed oxygen or hydrogen fuel cells that allow vessels to stay submerged for longer periods without surfacing.  AIP vessels are smaller than nuclear powered submarines, giving them greater access to shallow, littoral waters. For nations that are unable or unwilling to develop nuclear powered submarines, AIP offers an attractive alternative that improves submarine performance without the financial or political costs of nuclear propulsion.
Implications for Regional Stability
New capabilities for conventionally-powered submarines, such as AIP technology and cruise missile delivery systems, have heightened concern that nuclear armed states outside the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), such as Israel, India, and Pakistan, could mount nuclear warheads on submarine launched delivery systems.  Taking the example of the NPT-recognized nuclear weapon states, non-NPT nuclear weapon states hope to ensure the survival of their nuclear deterrent in the event of attack. Although such sea-based deployments may increase stability by ensuring a second-strike capability, they also have the potential to trigger arms races that create greater instability. Additionally, some experts are concerned that mounting nuclear weapons on submarines increases their vulnerability to terrorist attack, and that states may lack sufficient command—and—control to reliably manage a submarine—based nuclear force.  The proliferation of conventional submarines, even among states that do not possess a nuclear weapons capability, may also precipitate regional arms races.
Despite the advent of AIP technology, a number of states continue to pursue nuclear propulsion, often for reasons of national prestige or arms race dynamics. India and Brazil have taken significant steps toward this goal. After years of development, India officially commissioned its first nuclear-powered ballistic missile submarine, the INS Arinhart, in August 2016.  India has also leased a nuclear-powered attack submarine, the INS Chakra, from Russia.  By comparison, Brazil's development of a nuclear-powered submarine is far behind India's, and has a target launch date of 2025. 
In their bids to develop nuclear propulsion, both India and Brazil have received assistance from other states. Russia has been India's key partner, while France is assisting Brazil in constructing the hull for its first nuclear vessel.  Any spread of naval nuclear technology creates proliferation concerns due to a loophole in the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). This loophole allows states to withdraw fissile material from international safeguards if it is to be used for military reactor fuel, thus creating the possibility that fissile material could be diverted to a nuclear weapons program. 
When considering the export of submarines, states often prioritize financial gain over security concerns because of the lucrative nature of construction contracts. Russia's provision of nuclear reactor and submarine-design technology to China and India are examples of this phenomenon.  Additionally, multilateral export control regimes contain few restrictions on the sale of submarines, partly because they have historically been used for defensive purposes. The UN Arms Register requires states to declare the transfer of warships that displace 500 metric tons, or are able to fire missiles or torpedoes with a range of 25 kilometers or more.  The Wassenaar Arrangement goes further by requiring states to report the sale of vessels that displace 150 tons, as well as those that are equipped to fire missiles or torpedoes with a range of 25 kilometers.  However, declarations to the United Nations have not been comprehensive, and neither of these regimes bans the sale of any type of submarine.  The NPT also allows the export of nuclear submarines, as nuclear propulsion is viewed as an acceptable use of nuclear energy. As a result, there is little to prevent states from selling submarines to countries located in regions of high political and military tension.
 James Clay Moltz, "Global Submarine Proliferation: Emerging Trends and Problems," Nuclear Threat Initiative Issue Brief, March 2006, www.nti.org.
 "Agosta SSK," DCNS, www.dcnsgroup.com; "Israel buys two nuclear-capable submarines," The Washington Post, 25 August 2006, www.washingtonpost.com.
 "Submarines," Howaldtswerke-Deutsche Werft, www.hdw.de; Pierre Tran, "DCNS Pins Hopes on Exports," Defense News, 8 November 2010, www.defensenews.com.
 Chen Qingqing, “China exporting more submarines,” Global Times, 27 March 2017, Globaltimes.cn.
 Franz-Stefan Gady, "South Korea Launches 2nd Indonesian Attack Submarine," The Diplomat, 24 October 2016, http://thediplomat.com.
 "Brazil and France in Deal for SSKs, SSN," Defense Industry Daily, 12 December 2014, www.defenseindustrydaily.com.
 Milan Vego, "The Right Submarine for Lurking in the Littorals," U.S. Naval Institute, Proceedings Magazine, June 2010, Vol. 136, p. 6.
 "Sub Proliferation Sends Navies Diving for Cover," Jane's International Defence Review, 1 August 1997.
 James Clay Moltz, "Serious Gaps Emerging in Export Controls on Submarines," NIS Export Control Observer, produced by the James Martin Center for Nonproliferation Studies, June 2005, p. 23.
 Panda and Vipin Narang, "Pakistan Tests New Sub-Launched Nuclear-Capable Cruise Missile. What Now?" The Diplomat, 10 January 2017, http://thediplomat.com.
 Stefan Gady, “India Quietly Commissions Deadliest Sub,” The Diplomat, 19 October 2017, www.thediplomat.com.
 “India to get Russian nuclear submarine for 10-year lease,” RIA Novosti, 17 March 2010, www.rian.ru.
 Wilder Alejandro Sanchez, “The Status of Brazil’s Ambitious Prosub Program,” Center for International Maritime Security, 22 November 2016, www.cimsec.org.
 "Brazilian Submarines: DCNS Passes Major Milestone Towards One of Group's Biggest Contracts Ever," 7 September 2009, www.dcnsgroup.com; "Acordo Entre o Governo da República Federativa do Brasil e o Governo da República Francesa na Area de Submarinos" [Agreement Between the Government of the Federative Republic of Brazil and the Government of France in the Area of Submarines], Brazilian Defense Ministry, 23 December 2008, www.defesanet.com.br.
 Chunyan Ma and Frank von Hippel, "Ending the Production of Highly Enriched Uranium for Naval Reactors, Nonproliferation Review, Spring 2001, p. 87.
 James C. Bussert, "China Copies Russian Ship Technology for Use and Profit," Signal Online, June 2008, www.afcea.org.
 "Considerations for Reducing the Benchmark Range for Torpedoes on Warships of Less Than 500 Metric Tons," 2009 Group of Governmental Experts on the UN Register of Conventional Arms, United Nations Office of Disarmament Affairs, www.un.org.
 "Wassenaar Arrangement on Export Controls for Conventional Arms and Dual-Use Goods and Technologies," July 2004, www.wasenaar.org.
 James Clay Moltz, "Serious Gaps Emerging in Export Controls on Submarines," NIS Export Control Observer, produced by the James Martin Center for Nonproliferation Studies, June 2005, p. 24.
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The submarine proliferation resource collection is designed to highlight global trends in the sale and acquisition of diesel- and nuclear-powered submarines. It is structured on a country-by-country basis, with each country profile consisting of information on capabilities, imports and exports.
This material is produced independently for NTI by the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2018.