Submarine proliferation impacts both regional stability and the ability of states to deliver weapons of mass destruction (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. This is due largely to ongoing regional tensions in the Middle East, and both South and East Asia, which have driven submarine procurement. In this database, two specific trends are examined: the spread of nuclear propulsion technology beyond the five recognized nuclear weapon states, and the conventional submarine procurement programs of countries that may or may not have WMD capabilities. An additional issue, and one that has increased the demand for diesel-powered submarines, is the advent of Air Independent Propulsion (AIP) technology, which allows non-nuclear submarines to stay submerged for longer periods of time, thereby increasing performance and survivability. The use and spread of AIP technology is also examined in this database.
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 that have been involved in the export of conventional boats to some 14 navies around the world. Notable recipients of Russian diesel-powered submarines include China, Iran, and India. China and India, in particular, have purchased large numbers of Russian Kilo-class vessels over the last two decades.  As Japan has eased its ban on military exports, Tokyo has emerged as a challenger to the existing submarine market’s status quo. As of mid-2015, Japan had entered bids, which the country is expected to win, to update the Australian, Indian, and Thai submarine fleets. 
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 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 their 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 the need for external sources of oxygen.  The smaller size of AIP vessels also gives them greater access to littoral waters than their larger, nuclear-powered, counterparts. For nations that are unable, or unwilling, to develop nuclear powered submarines, AIP offers an attractive alternative that gives improved submarine performance without the financial cost of pursuing nuclear propulsion. For this reason, AIP technology has been popular with small navies that wish to gain greater underwater endurance.
Implications for Regional Stability
The increased endurance and survivability that AIP technology provides has heightened concern that nuclear armed states such as Israel, India and Pakistan could mount warheads on submarine launched delivery systems. An issue that is particularly troubling for regional stability is the proliferation of submarines capable of firing advanced cruise missiles.  Such concerns are especially relevant to South Asia and the Middle East, where the deployment of submarines carrying nuclear warheads may intensify regional arms races. Furthermore, an increased reliance on submarine-based delivery platforms among recognized nuclear weapon states such as the United Kingdom and France has only strengthened the argument that submarines offer increased survivability, and therefore, an assured second-strike capability. As a result, there is now a trend towards greater sea-based deployment of nuclear weapons among nuclear weapon states outside the NPT, such as India and Israel. In fact, it is rumored that the Israeli Navy has mounted nuclear-tipped cruise missiles on the Dolphin-class submarines it acquired from Germany.  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. The proliferation of conventional nuclear submarines, even among states that do not possess a nuclear weapons capability, may precipitate regional conventional 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. Although India began work on its so-called Advanced Technology Vessel (ATV) in the 1970s, the project ran into a number of financial and technical difficulties.  In July 2009, however, India launched its first ATV submarine, the INS Arihant, at the Ship Building Centre in Vishakapatnam.  The vessel is undergoing extensive sea trials before being commissioned into the Indian Navy, which has been delayed until 2016.  New Delhi plans eventually to build a fleet of three ballistic missile submarines (SSBNs) that will perform a strategic nuclear role, with each vessel likely to carry 12 Sagarika submarine launched ballistic missiles (SLBM).  By comparison, Brazil's development of a nuclear-powered submarine is far behind India's, and has a target launch date of 2025.  Between 1980 and 2005 Brazil invested heavily in the development of uranium enrichment, fuel fabrication and reactor technology, and is now in the final development stages of its Pressurized Water Reactor, the RENAP-11.  
In their bids to develop nuclear propulsion both India and Brazil are receiving assistance — to varying degrees — from other states. Russia has been India's key partner. In addition to Russia's export of nuclear reactor technology to India, the Soviet Union leased a Project 670 nuclear-powered cruise missile submarine to New Delhi in 1988.  The vessel's reactor was operated by Russian crew, and the submarine was returned to the Soviet Union in 1991. Due to delays in its indigenous program, India signed an agreement with Russia in 2004 to lease another nuclear-powered attack submarine, a Project 971 Shchuka-B (NATO designation Akula II), inducted into the Indian Navy as the INS Chakra in April 2012. 
Meanwhile, France is assisting Brazil in constructing the hull for its first nuclear vessel. Brasilia originally approached both Russia and France as possible suppliers, but eventually signed a contract with France in September 2009. The contract states that France will supply Brazil with the hull for a nuclear vessel on the condition that Brazil will be solely responsible for the vessel's nuclear components.  Any spread of naval nuclear technology beyond these two states creates nonproliferation 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 will 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 clear examples.  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.
 "Russian arms exports to China may drop significantly," RIA Novosti, 4 February 2009, www.rian.ru; "Submarine Forces: India," Jane's Underwater Warfare Systems, 11 November 2009, www.janes.com.
 Kyle Mizokami, "Japan's Emergence Defense Industry," U.S. Naval Institute, February 25, 2015, www.usni.org.
 "Brazil and France in Deal for SSKs, SSN," Defense Industry Daily, December 12, 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.
 "Israel buys two nuclear-capable submarines," The Washington Post, 25 August 2006, www.washingtonpost.com; 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.
 T.S. Gopi Rethinaraj, "ATV: All at Sea Before It Hits the Water," Jane's Intelligence Review, 1 June 1998.
 "Submarine Forces, India," Jane's Underwater Warfare Systems, 14 August 2009, www.janes.com.
 Amit Saksena, "Can India Accommodate the INS Arihant?" The Diplomat, January 26, 2015, thediplomat.com.
 Rajat Pandit, "Strategic Karwar Naval Base Set for Major Expansion," The Times of India, 20 May 2012, articles.timesofindia.indiatimes.com; Peter Crail and Eben Lindsey, "India Launches First Nuclear Submarine," Arms Control Today, September 2009, www.armscontrol.org.
 "Brazil to Join Elite Club of Nations Building Nuclear-Powered Submarines," Agence France-Presse, June 5, 2014, www.scmp.com.
 "Project 670 Skat," Federation of American Scientists, www.fas.org.
 "Brazil Accelerates Reactor Work for Nuclear Submarine Program," Sea Power, Vol. 47, No. 7 (July 2004), p. 44; in ProQuest Information and Learning Company, http://proquest.umi.com; "Programa de “Submarinos e Submarinos Nucleares de Ataque(SNA) da Marinha do Brasil," www.infomarmb.hpg.ig.com.br.
 "India to get Russian nuclear submarine for 10-year lease," RIA Novosti, 17 March 2010, www.rian.ru.
 "India Inducts Russian Made Nuclear Submarine into Navy," The Times of India, 4 April 2012, http://articles.timesofindia.indiatimes.com; Sarah Diehl and Eduardo Fujii, "Brazil's Pursuit of a Nuclear Submarine Raises Proliferation Concerns," WMD Insights, March 2008, www.wmdinsights.com.
 "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 and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2016.