Fact Sheet

United States Nuclear Overview

United States Nuclear Overview

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Background

This page is part of the United States Country Profile.

The United States became the world’s first nuclear weapon state in 1945, and remains the only state ever to have used a nuclear weapon in wartime. Today, it maintains one of the world’s largest operational arsenals: approximately 4,480 warheads, 1,740 of which are deployed. 1

This includes an estimated 1,590 strategic warheads based in the United States and 150 nonstrategic warheads deployed in Europe, as well as 700 deployed delivery systems (i.e., intercontinental ballistic missiles (ICBMs), submarine launched ballistic missiles (SLBMs), and strategic bombers). 2

President Barack Obama declared in his 2009 Prague address that because of its central role in nuclear weapons development, the United States has a “moral responsibility” to lead global efforts seeking “the peace and security of a world without nuclear weapons.” 3 The United States was a driving force behind the negotiation of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), as well as most other major arms control and nonproliferation treaties and regimes. Under the terms of the New Strategic Arms Reduction Treaty (New START) with Russia, signed in April 2010, the United States will reduce its strategic nuclear arsenal to 1,550 operational warheads deployed on 700 delivery vehicles by February 2018. The Obama administration remained committed to advancing the goal of nuclear disarmament as declared in Prague, and in accordance with U.S. NPT commitments.

The Donald Trump administration has not formally outlined its stance on nuclear disarmament and modernization. Personal comments made by President Trump indicate a desire to expand modernization plans initiated by the Obama administration and to renegotiate essential arms control treaties with Russia, such as the Intermediate-Range Nuclear Forces (INF) Treaty and the New START Treaty. On 27 January 2017, President Trump tasked the Department of Defense with conducting a Nuclear Posture Review, to be completed by 2018, which should clarify U.S. nuclear policy under the Trump administration. 4

In addition to its nuclear weapon capabilities, the United States is the world’s largest producer of nuclear power, accounting for more than 30 percent of the world’s nuclear generated electricity, with 99 operating nuclear power reactors, four under construction, and at least four other nuclear reactor licenses approved or awaiting approval. 5 The four nuclear reactors under construction are currently in limbo, as the company managing their construction, Westinghouse Electricity Co., filed for bankruptcy in March 2017. 6

Nuclear Capabilities

Strategic Nuclear Weapons

According to the most recent New START data exchange (1 March 2017), the United States deploys 1,411 strategic warheads on 673 Minuteman ICBMs, Trident II D-5 SLBMs, and B-52H and B-2A bombers. 7 The actual number of deployed U.S. warheads is likely higher since the treaty counts one strategic bomber as one operationally deployed warhead even though, for example, the B-2 bomber can carry up to 16 warheads. 8 A December 2016 estimate by Hans Kristensen and Robert Norris put the actual number of operational U.S. strategic warheads at roughly 1,590. 9

Land-based

400 ICBMs are deployed at three different Air Force bases, each with three squadrons that control 50 missile silos apiece—50 silos, scattered throughout the bases, are empty but ready to load stored missiles if necessary. The three bases operate the ICBMs from five launch control centers located in Colorado, Nebraska, Wyoming, North Dakota, and Montana. 10 There are an additional 270 non-deployed Minuteman ICBMs in storage. 11 Under normal circumstances, deployed missiles carry a single 300-335 kiloton warhead (W78 or W87), though about half are capable of being MIRVed—that is, they can carry multiple independently targetable re-entry vehicles. 12

To meet New START levels, the Air Force reduced the ICBM force to from 450 to 400 deployed missiles. The last of the 50 Minuteman III ICBMs slated for removal was taken out of its silo at F.E. Warren AFB on 2 June 2017. 13 The 50 excess silos will be kept “warm” if it becomes necessary to reload the missiles. 14 Under New START, the Air Force must destroy all previously deactivated ICBM silos. By August 2014, the Air Force had destroyed 103 deactivated silos. 15 50 silos at F.E. Warren Air Force Base in Wyoming and four silos at Vandenberg Air Force Base in California are awaiting dismantlement. 16

Air-based

The Air Force currently operates 18 B-2s and 70 B-52Hs that are nuclear capable. To comply with New START requirements limiting the United States to 60 nuclear-assigned bombers, only 16 B-2A and 44 B-52H strategic bombers have a nuclear mission on any given day. 17 The Air Force has extended the operational lifetime of its B-52s to 2040 and its B-2A’s to 2058, though the actual number of years they remain in service will depend on future congressional appropriations. 18 B-52s carry air-launched cruise missiles (ALCMs), while the B-2s carry B61 and B83 gravity bombs (with a yield of 1.2 megatons, the B83 is the largest nuclear weapon remaining in the U.S. arsenal). It is estimated that about 1,000 nuclear weapons are assigned to the U.S. bomber force, but only 300 are typically deployed. 19

Sea-based

The Navy’s 14 Ohio-class nuclear-powered ballistic missile submarines (SSBNs) carry Trident II D5 SLBMs. The D5 SLBM will be replaced in 2017 by “D5LE” missiles with greater longevity, accuracy, and flexibility. The D5LE will arm the Ohio-class submarines until the end of their service life in 2042. 20 Of the 14 submarines, 12 are considered operational; however minor repairs and an overhaul rotation mean that only 8-10 are at sea at any given time. 21 In keeping with New START obligations, by 2018 the Navy will reduce the number of deployed SLBMs to 240 by deactivating 4 of the 24 missiles tubes on each SSBN. 22 Ten submarines have been converted so far, and the remaining 4 will be converted in 2017. 23 The Trident II D5 SLBMs can carry up to 8 warheads each, but are thought on average to carry 4-5 warheads consisting of two basic types – the 100kt W76-0 and the 455kt W88. 24

Currently, each SSBN conducts, on average, two to three patrols a year (down from three to four patrols a decade ago), with an average patrol lasting 77 days. Most patrols now occur in the Pacific Ocean, possibly reflecting U.S. nuclear war planning vis-a-vis China, North Korea, and Russia. 25

Nonstrategic Nuclear Weapons

The U.S. inventory of nonstrategic (or tactical) nuclear weapons consists of approximately 500 B61 gravity bombs, 150 of which are deployed in Europe at six bases in the remaining North Atlantic Treaty Organization (NATO) states that host them: Belgium, Germany, Italy, the Netherlands, and Turkey. 26

Nuclear Force Modernization

The United States is currently modernizing its entire nuclear arsenal. In 2015, the United States completed a program to upgrade and extend the lifetime of its Minuteman III ICBMs through 2030. 27 In addition, the Air Force requested $9.4 billion to study a replacement for these missiles in 2013 and a $7 billion program was approved, including options to “increase survivability and reduce the requirement to keep missiles on high alert.” 28 In 2016, a program was approved to move development of this new ground-based strategic deterrent into the “Technology Maturation and Risk Reduction” phase. 29 The Air Force also aims to replace the current strategic bomber fleet with a new Long-Range Strike Bomber (LRS-B). The LRS-B is scheduled to begin flight testing in the mid-2020s with an anticipated operational capability toward the end of the decade. 30 The United States also plans to “upgrade nuclear command and control capabilities on existing bombers; develop improved nuclear weapons (B61-12s and long-range standoff missiles, or LRSOs); and design a new heavy bomber.” 31

With respect to the sea-based leg of the Nuclear Triad, the United States intends to replace its Ohio-class SSBNs with the next-generation Columbia-class in the 2020s. The Columbia-class will be 2,000 tons heavier and equipped with only 16 missile tubes. Procurement of the first submarine is slated for 2021 and its deployment is slated for 2031. 32 Each new SSBN is currently estimated to cost up to $8.6 billion, a price tag that many fear will consume the Navy’s entire shipbuilding budget and consequently reduce the U.S. global presence. 33

The National Nuclear Security Administration (NNSA) has also outlined a “3+2 Plan” to modernize the U.S. stockpile of nuclear warheads. 34 Under the plan, sea- and land-based ballistic missiles would use any of three “inter-operable warheads,” and air-delivered weapons would use one of two warheads. In addition, the family of B61 bombs currently assigned to strategic bombers as well as dual-capable aircraft in Europe will be consolidated into one upgraded version known as the B61-12. 35

An official estimate by the Congressional Budget Office (CBO) puts the cost of the DoD’s and DoE’s modernization plans at $400 billion over the next ten years. 36 The CBO breaks this estimate down as follows: $189 billion for strategic nuclear delivery systems, $9 billion for tactical nuclear delivery systems and weapons, $87 billion for DoE’s nuclear weapons labs, $58 billion for DoD’s command and control, and $56 billion to account for unanticipated cost increases. 37 The Arms Control Association estimated total modernization costs by type, projecting the costs of modernizing the SLBM fleet at $130 billion, the new bomber fleet around $100 billion, the new ICBMs around $90-140, and the new ALCMs about $11 billion. 38 The DoD and NNSA’s internal estimates are significantly lower, projecting $230-290 billion and $300 billion, respectively, spread over the next 25 years. 39 However, one group of experts extrapolates the thirty-year cost of maintaining and upgrading existing nuclear bombs and warheads at over $1 trillion. 40

The Obama administration pushed back against critics of nuclear modernization, emphasizing that there is no contradiction between nuclear force modernization and the vision of a world free of nuclear weapons. It maintained that modernization is important to increasing the safety, security, and reliability of nuclear weapons, as well as ensuring the credibility of extended deterrence. 41 The Trump administration’s 2018 budget proposal allocates an extra $589 million dollars for nuclear force modernization. The additional funding reflects the increasing costs of the existing modernization plan set out by the Obama administration, rather than an expansion of that plan. 42

Evolution of U.S. Nuclear Doctrine

U.S. nuclear doctrine has gone through several distinct phases, but while the declaratory policy (what is said publicly) has shifted over time, operational policy was relatively consistent throughout the Cold War. 43 This included striking first if necessary (preemptive attack) in order to prevent the Soviet Union from launching an attack that would have precluded any coordinated, effective U.S. response. Importantly, however, the decision to use nuclear weapons has always been the president’s alone to make (apart from the pre-delegated authority to use certain air defense nuclear weapons or nonstrategic nuclear weapons allocated to NATO under very limited emergency circumstances first authorized by President Eisenhower in the late 1950s). 44

Massive Retaliation

Early plans for nuclear war envisioned nuclear weapons as larger versions of the conventional bombs that had helped the United States to win WWII. In the days of the U.S. nuclear monopoly, if the Soviet Union had attempted to overrun Europe or challenge the United States elsewhere in the world, U.S. bombers (the only delivery system capable of carrying the very large bombs of the time) would have dropped nuclear weapons on the Soviet Union until it capitulated or was destroyed. By the early 1950s, once the Soviets were believed to have deployed significant numbers of atomic bombs of their own, nuclear deterrence began to take shape. Although the United States never ruled out striking first, the difficulty of ensuring the destruction of every Soviet nuclear weapon called for a new approach. Thus the Eisenhower administration announced in 1954 that Soviet aggression anywhere in the world would be met with massive retaliation, an unleashing of the U.S. nuclear arsenal against Soviet nuclear forces and urban and industrial targets.

Until 1960, there was no unified nuclear war plan. The Air Force, Navy, and Army, through their various commands, developed their own target maps and attack plans. Not surprisingly, this resulted in a significant degree of redundancy, with the military devoting more firepower than was actually necessary to destroy particular targets. Worse still, under the plans then in effect one service’s weapons would have destroyed another’s in any nuclear conflict, limiting the damage to the intended Soviet targets. Dissatisfied with this state of affairs, Eisenhower in 1960 ordered the creation of the Joint Strategic Target Planning Staff to develop a unified nuclear war plan.

Flexible Response

But the early unified plans still envisioned a massive strike. Doctrinal and technological limitations did not permit any flexibility. If the order for a nuclear strike had been given, almost nothing would have been withheld, regardless of the nature of the initial attack. Early plans called for attacks on targets in the Warsaw Pact and China even if they were not involved in the confrontation. This concerned President Kennedy greatly, so efforts were made to develop a more flexible range of options for the president, theoretically better suited to managing escalation in situations short of global nuclear war. In an effort to control the escalation of a nuclear conflict, options were also developed that distinguished between military targets (counterforce) and civilian and industrial targets (countervalue). In reality, the scale of damage made possible by nuclear weapons and the proximity of military targets to civilian populations would have made such distinctions meaningless in many scenarios. However, flexible response was designed to give the U.S. president nuclear options that could potentially prevent escalation into all-out nuclear warfare.

Mutual Assured Destruction (MAD)

Once the United States believed the Soviet Union had amassed enough nuclear weapons to make a preemptive attack all but impossible, U.S. strategic thinking began to shift from destruction to deterrence. If the United States could credibly threaten to destroy the Soviet Union—regardless of which country struck first—then in theory, the Soviet Union would have no incentive to launch a nuclear first strike. Robert McNamara (President Kennedy’s and then President Lyndon Johnson’s secretary of defense), developed multiple formulas for assured destruction, calculating what percentage of the Soviet military, industry, and population would have to be under credible threat of annihilation for deterrence to work. Importantly, these calculations (like all earlier ones and even those in use today), considered only the blast effects of a nuclear explosion. Significant secondary effects, such as radiation and mass fire, were excluded based on military planners’ perceptions that they would be too difficult to accurately predict. Therefore, as Lynn Eden’s groundbreaking study concluded, U.S. nuclear war plans have consistently underestimated the physical destruction and human casualties that would be caused by even a limited nuclear attack. 45

Limited Nuclear War

By the early 1970s, U.S. policymakers feared that deterrence was weakening, and that MAD was no longer credible, especially in the context of a smaller-scale attack on NATO. The Nixon administration sought to bolster deterrence by creating options for limited nuclear war. This was an outgrowth of the earlier flexible response doctrine. There were also growing concerns that the Soviet nuclear arsenal might be approaching levels and capabilities that could enable the USSR to contemplate a successful first strike on the United States. This led to a renewed emphasis on counterforce targeting, including the deployment of multiple independently targetable re-entry vehicles (MIRVs) for ballistic missiles (which would enable one missile to destroy several others and increase the number of targets that could be covered without requiring the United States to use all its missiles). However, MIRVed missiles also created the destabilizing incentive for an adversary to launch a pre-emptive strike.

The Carter and Reagan administrations built on these efforts, with the Reagan administration implementing plans to “prevail” in a protracted nuclear war with the Soviet Union. Significant efforts were also made to convince the Soviet Union that no use of nuclear weapons, on any scale or for any reason, would enable a Soviet victory, regardless of how the USSR defined victory. Denying the Soviet Union the ability to use its nuclear weapons to attain military gain was considered essential to preventing a nuclear war in the first place.

Counterproliferation and Beyond

The end of the Cold War diminished concerns about an intentional nuclear war between the superpowers, but even as the number of U.S. nuclear weapons declined dramatically—from 21,392 operational weapons in 1990 to fewer than 4,500 today—there was no wholesale rethinking of the purpose of the U.S. nuclear arsenal. The Clinton administration instituted a symbolic de-targeting plan that kept wartime targets out of ICBM guidance systems in peacetime, so that in the event of an accidental launch they would only strike the ocean. The George W. Bush administration took a different and controversial approach, however, returning China to the U.S. nuclear war plan (it had been removed by the Reagan administration) and indicating in its Nuclear Posture Review (NPR) that the United States would consider using nuclear weapons in a broad range of “rogue state” scenarios.

The Obama administration returned to a more conservative approach to nuclear doctrine in its 2010 NPR. But even as President Obama embraced the goal of seeking a world without nuclear weapons, and negotiated an arms reduction treaty with Russia, his administration did not make fundamental changes to U.S. nuclear doctrine. On 19 June 2013, more than two years after releasing its NPR, the administration released an unclassified summary of its “Nuclear Weapons Employment Strategy,” which “affirms that the United States will maintain a credible deterrent, capable of convincing any potential adversary that the adverse consequences of attacking the United States or our allies and partners far outweigh any potential benefit they may seek to gain through an attack.” 46 While continuing to express its intention to reduce the role of nuclear weapons, the Obama administration declined to specify that the sole purpose of the U.S. nuclear arsenal was to deter or respond to a nuclear attack. Instead the new strategy said that the “the United States will only consider the use of nuclear weapons in extreme circumstances to defend the vital interests of the United States or its allies and partners. The guidance narrowed U.S. nuclear strategy to focus on only those objectives and missions that are necessary for deterrence in the 21st century. In so doing, the guidance took further steps toward reducing the role of nuclear weapons in our security strategy.” 47

Statements made by President Trump seem to indicate a personal desire for an expansion of the U.S. nuclear arsenal, which would be a reversal from decades of reductions in U.S. nuclear weapons. However, a new Nuclear Posture Review is underway and its completion in 2018 will set out a clearer and more detailed plan for U.S. nuclear strategy under President Trump. 48

History of the Nuclear Weapons Program

The Manhattan Project

Fearful of Nazi Germany’s possible pursuit of the atomic bomb, President Franklin D. Roosevelt, at the urging of concerned scientists, authorized in 1940 the first government-funded research into the military potential of nuclear energy. To consolidate and coordinate the effort, the Manhattan Engineering District was established in 1942. Informally known as the Manhattan Project, this massively funded top-secret project was managed by the Army Corps of Engineers. It was led by Brigadier General Leslie R. Groves, with University of California-Berkeley physicist J. Robert Oppenheimer in charge of the scientific effort. The Manhattan Project brought together the country’s top physicists—alongside allied scientists from the United Kingdom and Canada—at a barren mesa in Los Alamos, New Mexico. The U.S. government also constructed massive industrial complexes in southeastern Washington State (to manufacture plutonium), and in a sparsely populated corner of Tennessee (to enrich uranium). These efforts to produce weapons-grade material consumed nearly all of the $2 billion (in then-year dollars) spent on the Manhattan Project. 49 Wartime personnel at the Oak Ridge site (as the Tennessee facilities came to be known) peaked at 75,000, almost none of whom knew that they were working to build a nuclear weapon. 50

At Los Alamos, the scientific teams decided on two different bomb designs: a gun-type weapon, which utilized highly enriched uranium, and an implosion weapon, which utilized plutonium. The latter design was used in the world’s first nuclear explosion—the Trinity test on 16 July 1945 near Alamogordo, New Mexico. The gun-type design was considered so reliable that it was never subjected to a full-scale test.

On 6 August 1945, the United States dropped a gun-type bomb nicknamed “Little Boy” over Hiroshima, Japan (with an estimated explosive yield of 15 kilotons), killing between 60,000 and 80,000 people immediately, and up to 50,000 more from injury and radiation by the end of 1945. The “Fat Man” bomb that destroyed Nagasaki on 9 August used the implosion design (estimated yield 21 kilotons), killing approximately 40,000 instantly and terminally injuring another 10,000.

Post-War Developments

After the war, there was substantial debate in Washington over whether the nuclear program should continue to be managed by the military or turned over to a civilian agency. This debate was resolved by the Atomic Energy Act of 1946, which transferred control of the U.S. atomic program to the new civilian Atomic Energy Commission (AEC), effective 1 January 1947. In 1953, President Dwight D. Eisenhower announced the Atoms for Peace program, through which the United States would, with requisite safeguards, promote the peaceful uses of nuclear technology, hoping that “the miraculous inventiveness of man shall not be dedicated to his death, but consecrated to his life.” 51 While Atoms for Peace established many of the key elements of the current nonproliferation regime, such as the International Atomic Energy Agency (IAEA) and the concept of safeguards, it also spread dual-use nuclear materials and technology around the world. Some recipients of Atoms for Peace assistance—such as India and South Africa—would divert peaceful U.S. nuclear assistance to military nuclear programs.

The Expansion of the Arsenal

The Cold War, which arguably began with the end of the Second World War, significantly intensified throughout the 1940s. By early 1950, the United States possessed more than 200 atomic bombs, but it no longer had monopoly control of nuclear weapons, as the Soviet Union had tested its first nuclear device in August 1949. Despite the emphatic opposition of some key nuclear scientists, including Albert Einstein and J. Robert Oppenheimer, the United States embarked on an accelerated program to develop the even more powerful hydrogen bomb. The AEC’s General Advisory Committee, which Oppenheimer chaired, recommended against hastily developing the hydrogen bomb, “argu(ing) that a higher morality should bar the pursuit of knowledge” of such a genocidal weapon. 52 Atomic weapons could sufficiently deter the use of the hydrogen bomb, the group reasoned, even if the Soviets developed one. 53 Ultimately, however, fearful of Soviet technological advances, the U.S. government moved forward with the hydrogen bomb program and detonated the first thermonuclear device on 1 November 1952 at Enewetak Atoll, with a yield of 10.4 megatons. On 1 March 1954 the United States detonated the first deliverable thermonuclear bomb at Bikini Atoll, the largest U.S. nuclear test ever at 15 megatons (greatly exceeding its predicted yield of 6 megatons). In close pursuit, the Soviets detonated their first true hydrogen bomb on 23 November 1955. 54

The hydrogen bomb project was part of the Eisenhower administration’s “New Look” military program, which emphasized mass production of nuclear weapons (and especially tactical nuclear weapons). Eisenhower favored nuclear over conventional weapons production, mistakenly believing a defense centered on nuclear weapons would be significantly less expensive than conventional weapons (the concept was promoted with the phrase “a bigger bang for a buck.”) 55 During peak production in 1959 and 1960, the United States built more than 7,000 new nuclear warheads and bombs a year—mostly tactical nuclear weapons—equaling a rate of approximately 20 weapons produced per day. 56 The stockpile reached a peak of more than 31,000 operational warheads and bombs in 1967, “because each military branch wanted a special nuclear weapon for practically every conceivable mission.” 57

By the early 1970s, the United States deployed more than 7,000 nuclear weapons in Europe—to be used in defending NATO—as well as more than 2,000 in the Pacific states, including Japan, Guam, and Taiwan. Aircraft carriers, cruisers, destroyers, frigates, and submarines routinely carried an additional 3,000 nuclear weapons, totaling 38 types of nuclear weapon systems deployed abroad. However, owing to strict U.S. operational secrecy the weapons’ host nations “did not always know they were there.” 58

Until 1964, two large gaseous diffusion plants produced the highly enriched uranium used in many of these weapons, the K-25 Plant at Oak Ridge and another facility in Portsmouth, Ohio. Fourteen different reactors in Washington State and South Carolina produced weapon-grade plutonium, though nine of these were shut down during the 1960s after officials determined they were no longer needed; the remaining five, which also produced tritium, did not cease production until 1987. Even with the high demand for nuclear weapons through the 1960s, as well as a renewed emphasis on nuclear weapons in the 1980s, the frenzied production of these fissile materials—which was not driven by any specified, finite requirement—grossly outpaced the military need for them (leading to long term and very expensive programs to “clean up” the facilities where fissile materials were manufactured and secure them against unauthorized use). In all, the United States produced 745.3 metric tons of plutonium and 103.5 metric tons of highly enriched uranium. The United States has not produced any fissile materials for nuclear weapons since 1987, and, even after downblending or marking for downblending about 141 tons of HEU, there is still a remaining stockpile of 194 tons of HEU and 49.3 tons of weapons-grade plutonium designated as excess for national security needs. 59

Arms Control and Disarmament

From the Trinity test of 1945 to the last U.S. test on 23 September 1992, the United States conducted 1,054 nuclear explosion tests in the atmosphere, above the atmosphere (exoatmospheric), underground, and underwater. 60

Following the Trinity test at Alamogordo, New Mexico, the first underwater nuclear explosion (part of the Crossroads series) took place in July 1946 at Bikini Atoll in the Marshall Islands. In 1951, eager to conduct more frequent tests and reduce the considerable costs associated with operating a test site in the Pacific Ocean, the AEC opened the Nevada Proving Ground (65 miles northwest of Las Vegas), where the majority of tests over the next 40 years would take place. Significantly, officials chose Nevada over other locations even though they understood that testing there would subject surrounding states (and indeed most of the rest of the country) to significant amounts of dangerous radioactive fallout. 61 Other locations of U.S. nuclear tests included the South Atlantic Ocean (1,110 miles southwest of South Africa), Christmas Island, Johnston Island, and various locations in Alaska, Colorado, Mississippi, Nevada, and New Mexico.

In the lead-up to what would become the Limited Nuclear Test Ban Treaty (LTBT), the United States observed a testing moratorium with the Soviet Union between November 1958 and September 1961. The LTBT, enacted in 1963 following the Cuban Missile Crisis and widespread protests about the effects of radioactive fallout from aboveground testing, barred all atmospheric, above-ground, underwater, and outer space nuclear testing by the signatories (the United States, the Soviet Union, and the United Kingdom. In a concession to the U.S. military and U.S. weapons developers, it did not prohibit underground testing.

The 1962 Cuban Missile Crisis, compounded by China’s entrance into the “nuclear club” in 1964, convinced the United States that nuclear weapons themselves—and not just the negative health and environmental consequences of their testing—had to be contained.

Inspired by Ireland’s General Assembly Resolution 1380 (XIV), the United States assumed leadership negotiating what would become the Treaty on the Non-Proliferation of Nuclear Weapons, or NPT. Signed in 1968, the NPT sought to prevent the further spread of nuclear weapons by enshrining a twofold bargain: the nuclear weapon states pledged to negotiate an early end to the arms race and to work towards nuclear disarmament (Article VI), in exchange for non-nuclear weapon states’ pledges to forego nuclear weapons of their own (Article II). Non-nuclear weapon states in compliance with the NPT were granted an “inalienable right” to “develop research, production and use of nuclear energy for peaceful purposes without discrimination” (Article IV). The NPT entered into force on 5 March 1970, and all but three states would eventually become a party to it. 62

With parties to the NPT required to ensure exports of certain nuclear-related goods to non-nuclear weapon states were subject to IAEA safeguards, the United States, along with fourteen other supplier states, met to create the Nuclear Exporters Committee (or Zangger Committee) in 1972. The Committee’s aim was to reach a common understanding on precisely what nuclear materials and related equipment should be subject to safeguards as a condition for supply. Following India’s peaceful nuclear explosion in 1974, the United States led the effort to establish the Nuclear Suppliers Group, a voluntary organization of 46 nuclear supplier states, to better coordinate members’ export control policies and control commerce in sensitive nuclear materials and technologies. 63

Even before the entry-into-force of the NPT, the United States and the Soviet Union began, in November 1969, negotiation of the Strategic Arms Limitation Talks (SALT). The SALT process produced the May 1972 Anti-Ballistic Missile Treaty, limiting strategic missile defenses to 200 interceptors and two sites each (later reduced to one site by a 1974 protocol; in December 2001, the George W. Bush administration notified Russia of its intention to withdraw from the ABM Treaty in order to deploy a missile defense system in Alaska and California). In an “Interim Agreement” both states also pledged not to construct new ICBM silos, not to increase the size of existing silos “significantly,” and to cap the number of nuclear-armed submarines and the number of launch tubes a nuclear-armed submarine could carry. 64

The second round of SALT talks, signed in June 1979, limited both sides to 2,250 delivery vehicles (e.g., an ICBM silo, an SLBM launch tube, or a heavy bomber). Both sides pledged to adhere to the SALT II agreement while awaiting its entry-into-force, and during this time, President Jimmy Carter sought to negotiate a Comprehensive Nuclear Test-Ban Treaty (CTBT). Both SALT II ratification and CTBT negotiations were shelved after the Soviet Union invaded Afghanistan.

Under President Ronald Reagan, who on 26 May 1986 announced he would no longer abide by the un-ratified SALT II agreement, the United States and the Soviet Union negotiated and signed the Intermediate-Range Nuclear Forces (INF) Treaty in 1987. The INF Treaty eliminated an entire class of weapon systems; all nuclear and conventional ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 kilometers were now prohibited. The Reagan administration also initiated talks on the Strategic Arms Reduction Treaty (START) process, which led to the 31 July 1991 signing of the first START Treaty, intended to limit each side’s delivery vehicles to 1,600 and its accountable warheads to 6,000, of which no more than 4,900 could be ballistic missile warheads (ICBMs and SLBMs); 1,540 on heavy missiles (a restriction on Russia‘s SS-18 ICBM); and 1,100 on mobile ICBMs. The entry-into-force of START I was delayed by the collapse of the Soviet Union, which occurred just four months after the treaty’s signature. START I provisions were ultimately implemented by December 2001.

At the Cold War’s end, Presidents George H.W. Bush and Mikhail Gorbachev sought a new arms control framework that would forgo lengthy arms control negotiations and ratifications in favor of “reciprocal unilateral commitments” that were politically, rather than legally, binding. This effort became known as the Presidential Nuclear Initiatives (PNIs). These commitments involved reducing nonstrategic or tactical nuclear weapons (TNWs) and delivery vehicles. They were non-verifiable, and potentially reversible, but led to the withdrawal of “perhaps 17,000 TNWs… the deepest reductions in nuclear arsenals to date.” 65

The Bill Clinton administration revived efforts to negotiate a CTBT. U.S. and Russian acceptance of a “zero yield” CTBT revived efforts at the Conference on Disarmament, which produced the basis for the treaty text in 1995, and a final treaty was approved by the General Assembly in 1996. In September of that year the United States became the first signatory to the CTBT, but the U.S. Senate rejected ratification in 1999, effectively halting global progress towards the treaty’s entry-into-force. 66

Efforts to ratify START II, which was signed in January 1993, were thwarted by the 2002 U.S. withdrawal from the ABM Treaty. In turn, the failure to ratify START II prevented the beginning of START III negotiations, which Presidents Bill Clinton and Boris Yeltsin had agreed to in March 1997. The START process was temporarily replaced by the 2002 Strategic Offensive Reduction Treaty (SORT, or Moscow Treaty), signed by Presidents George W. Bush and Vladimir Putin. But SORT lacked START’s specific counting rules, verification arrangements, and irreversibility. On 5 February 2011, New START replaced SORT.

While the Obama administration was committed to pursuing further reductions with Russia as part of its commitment to seeking “the security of a world without nuclear weapons,” Russia became reluctant to agree to any cuts below 1,000 weapons, suggesting that cooperative measures beyond strategic warhead counting—such as cooperation and/or limitations on missile defenses, space weapons, and other conventional weapon systems—would be required. 67

At the start of the Trump administration, Russia indicated that it would be willing to negotiate the extension of the New START Treaty in 2021. However, the future of the New START Treaty under Trump is unknown, as Trump has repeatedly called the Treaty “a bad deal” for the United States. 68 The future of the INF Treaty is also uncertain under the Trump administration. The House and Senate versions of the National Defense Authorization Act (NDAA) for FY18 seek to declare Russia in “material breach” of the INF Treaty and allocate millions in funding for the research and development of U.S. intermediate-range missile systems. 69

Civilian Nuclear Energy Program

Early Development, Current Status, Future Plans

The 1954 amendment to the Atomic Energy Act assigned the Atomic Energy Commission (AEC) the dual function of both promoting the use of nuclear power and regulating its safety. After increasing concerns over the AEC’s ability to simultaneously regulate and promote nuclear energy, Congress abolished the AEC in 1974. The 1974 Energy Reorganization Act established the Nuclear Regulatory Commission (NRC), which became operational on 19 January 1975, with a focus on radiation protection, reactor safety, and the licensing and regulation of nuclear materials, plant siting, and other environmental protections.

The first full-scale U.S. nuclear power plant came online on 2 December 1957, at the Shippingport Atomic Power Station, approximately 25 miles from Pittsburgh, PA. Significant nuclear power construction followed, but factors including the 1979 Three Mile Island accident in the United States and the 1986 Chernobyl disaster in 1986 effectively ended new U.S. nuclear plant construction throughout the 1980s, 1990s, and early 2000s.

There are currently 99 commercially operating nuclear power reactors in the United States (65 PWRs and 34 BWRs), providing nearly one-fifth of total U.S. commercial energy. 70 Four new reactors are under construction in Georgia and South Carolina. However, the company tasked with building the units, Westinghouse Electric Co., filed for bankruptcy in March 2017. 71 Westinghouse filed for bankruptcy due to issues managing the projects’ subcontractors, and is expected to break its contracts for constructing the Georgia and South Carolina plants. 72 Overall, the long-term future of nuclear energy in the United States is still up for debate. In addition to safety and nuclear security concerns, exacerbated by Japan’s 2011 Fukushima accident, the economic viability of nuclear power has been put into further doubt by the recent availability of cheap and abundant natural gas. 73

Cooperative Agreements

Since the Atomic Energy Act (AEA) of 1954 legalized nuclear commerce, the United States has undertaken civil nuclear cooperation with other countries. Section 123 of the AEA established nine nonproliferation criteria required of states seeking a so-called 123 nuclear cooperation agreement with the United States, an enabling agreement required for significant nuclear cooperation to take place between the United States and other countries. 74 As of January 2017, the United States has entered into nuclear cooperation agreements with 20 countries, as well as with the IAEA, the European Atomic Energy Community, and Taiwan. 75 A number of new and renewal agreements are in negotiation; as discussed in this NTI issue brief, significant debate remains ongoing over whether the nonproliferation pre-conditions for 123 nuclear cooperation agreements need strengthening.

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Glossary

Nuclear-weapon states (NWS)
NWS: As defined by Article IX, paragraph 3 of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the five states that detonated a nuclear device prior to 1 January 1967 (China, France, the Soviet Union, the United Kingdom, and the United States). Coincidentally, these five states are also permanent members of the UN Security Council. States that acquired and/or tested nuclear weapons subsequently are not internationally recognized as nuclear-weapon states.
Deployment
The positioning of military forces – conventional and/or nuclear – in conjunction with military planning.
Strategic nuclear warhead
Strategic nuclear warhead: A high-yield nuclear warhead placed on a long-range delivery system, such as a land-based intercontinental ballistic missile (ICBMs), a submarine-launched ballistic missile (SLBMs), or a strategic bomber.
Tactical nuclear weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-range missiles, deployed for use in battlefield operations.
Intercontinental ballistic missile (ICBM)
Intercontinental ballistic missile (ICBM): A ballistic missile with a range greater than 5,500 km. See entry for ballistic missile.
Submarine-launched ballistic missile (SLBM)
SLBM: A ballistic missile that is carried on and launched from a submarine.
Strategic Bomber
Strategic Bomber: A long-range aircraft designed to drop large amounts of explosive power—either conventional or nuclear—on enemy territory.
Prague Speech
Refers to the speech given by U.S. President Barack Obama in April 2009 at Hradcany Square, Prague, the Czech Republic. In the speech, Obama stated "America’s commitment to seek the peace and security of a world without nuclear weapons." He noted that “the United States will take concrete steps towards a world without nuclear weapons.” The Prague speech served as the framework for the 2010 Nuclear Posture Review and subsequent U.S. arms control efforts.
Treaty on the Non-Proliferation of Nuclear Weapons (NPT)
The NPT: Signed in 1968, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the most widely adhered-to international security agreement. The “three pillars” of the NPT are nuclear disarmament, nonproliferation, and peaceful uses of nuclear energy. Article VI of the NPT commits states possessing nuclear weapons to negotiate in good faith toward halting the arms race and the complete elimination of nuclear weapons. The Treaty stipulates that non-nuclear-weapon states will not seek to acquire nuclear weapons, and will accept International Atomic Energy Agency safeguards on their nuclear activities, while nuclear weapon states commit not to transfer nuclear weapons to other states. All states have a right to the peaceful use of nuclear energy, and should assist one another in its development. The NPT provides for conferences of member states to review treaty implementation at five-year intervals. Initially of a 25-year duration, the NPT was extended indefinitely in 1995. For additional information, see the NPT.
Nonproliferation
Nonproliferation: Measures to prevent the spread of biological, chemical, and/or nuclear weapons and their delivery systems. See entry for Proliferation.
New START
New START: A treaty between the United States and Russia on further limitations and reductions of strategic offensive weapons, signed on 8 April 2010, which entered into force on 5 February 2011. Under the New START provisions, the two sides have to reduce the number of deployed strategic warheads and the number of deployed strategic delivery vehicles within seven years of the treaty’s entry into force. The treaty’s verification measures are based on the earlier verification system created under START I. New START supersedes the Moscow Treaty, and its duration is 10 years, with an option of extension for up to five years. See entry for Strategic Arms Reduction Treaty and Treaty of Moscow. For additional information, see New START.
Disarmament
Though there is no agreed-upon legal definition of what disarmament entails within the context of international agreements, a general definition is the process of reducing the quantity and/or capabilities of military weapons and/or military forces.
Intermediate-Range Nuclear Forces (INF) Treaty
A treaty between the United States and the former Soviet Union, signed on 8 December 1987, which entered into force on 1 June 1988. It aimed to eliminate and ban all ground-launched ballistic and cruise missiles with a range of between 300 and 3,400 miles (500 to 5,500 kilometers). The treaty required the United States and the Soviet Union to conduct inspections at each other's sites during the elimination of treaty-limited items (TLI). By May 1991, all intermediate-range and shorter-range missiles, launchers, related support equipment, and support structures were eliminated. For additional information, see the INF Treaty.
Nuclear Posture Review
Under a mandate from the U.S. Congress, the Department of Defense regularly conducts a comprehensive Nuclear Posture Review to set forth the direction of U.S. nuclear weapons policies. To date, the United States has completed four Nuclear Posture Reviews (in 1994, 2001, 2010, and 2018).
Nuclear energy
Nuclear energy: The energy liberated by a nuclear reaction (fission or fusion), or by radioactive decay.
Nuclear reactor
Nuclear reactor: A vessel in which nuclear fission may be sustained and controlled in a chain nuclear reaction. The varieties are many, but all incorporate certain features, including: fissionable or fissile fuel; a moderating material (unless the reactor is operated on fast neutrons); a reflector to conserve escaping neutrons; provisions of removal of heat; measuring and controlling instruments; and protective devices.
Bomber
An aircraft carrying conventional or nuclear bombs, or conventionally or nuclear-armed cruise missiles, for use against ground or sea targets.
Silo
Hardened underground facility for housing and launching a ballistic missile.
Kiloton
Kiloton: A term used to quantify the energy of a nuclear explosion that is equivalent to the explosion of 1,000 tons of trinitrotoluene (TNT) conventional explosive.
Multiple Independently-targetable Reentry Vehicle (MIRV)
An offensive ballistic missile system with multiple warheads, each of which can strike a separate target and can be launched by a single booster rocket.
Reentry Vehicle (RV)
A nuclear warhead on a ballistic missile specially designed to reenter the earth's atmosphere in the terminal portion of the missile's trajectory.
Dismantlement
Dismantlement: Taking apart a weapon, facility, or other item so that it is no longer functional.
Air-Launched Cruise Missile (ALCM)
A missile designed to be launched from an aircraft and jet-engine powered throughout its flight. As with all cruise missiles, its range is a function of payload, propulsion, and fuel volume, and can thus vary greatly. Under the START I Treaty, the term "long-range ALCM" means an air-launched cruise missile with a range in excess of 600 kilometers.
Megaton (MT)
Megaton (MT): The energy equivalent released by 1,000 kilotons (1,000,000 tons) of trinitrotoluene (TNT) explosive. Typically used as the unit of measurement to express the amount of energy released by a nuclear bomb.
Ballistic missile
A delivery vehicle powered by a liquid or solid fueled rocket that primarily travels in a ballistic (free-fall) trajectory.  The flight of a ballistic missile includes three phases: 1) boost phase, where the rocket generates thrust to launch the missile into flight; 2) midcourse phase, where the missile coasts in an arc under the influence of gravity; and 3) terminal phase, in which the missile descends towards its target.  Ballistic missiles can be characterized by three key parameters - range, payload, and Circular Error Probable (CEP), or targeting precision.  Ballistic missiles are primarily intended for use against ground targets.
SSBN
Ship, Submersible, Ballistic, Nuclear: A hull classification for a submarine capable of launching a ballistic missile. The "N", or nuclear, refers to the ship's propulsion system. SSBN's are generally reserved for strategic vessels, as most submarine launched ballistic missiles carry nuclear payloads. A non-strategic vessel carries the designation SSN, or attack submarine.
Submarine-launched ballistic missile (SLBM)
SLBM: A ballistic missile that is carried on and launched from a submarine.
Tactical nuclear weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-range missiles, deployed for use in battlefield operations.
North Atlantic Treaty Organization (NATO)
The North Atlantic Treaty Organization is a military alliance that was formed in 1949 to help deter the Soviet Union from attacking Europe. The Alliance is based on the North Atlantic Treaty, which was signed in Washington on 4 April 1949. The treaty originally created an alliance of 10 European and two North American independent states, but today NATO has 28 members who have committed to maintaining and developing their defense capabilities, to consulting on issues of mutual security concern, and to the principle of collective self-defense. NATO is also engaged in out-of-area security operations, most notably in Afghanistan, where Alliance forces operate alongside other non-NATO countries as part of the International Security Assistance Force (ISAF). For additional information, see NATO.
Deterrence
The actions of a state or group of states to dissuade a potential adversary from initiating an attack or conflict through the credible threat of retaliation. To be effective, a deterrence strategy should demonstrate to an adversary that the costs of an attack would outweigh any potential gains. See entries for Extended deterrence and nuclear deterrence.
Extended deterrence
Extended deterrence: A country protected from potential adversaries by the nuclear weapons’ backed security guarantee of an ally is said to be under an (extended deterrence) nuclear umbrella. See entry for Deterrence.
Nuclear (use) doctrine
Nuclear (use) doctrine: The fundamental principles by which a country’s political or military leaders guide their decision-making regarding the conditions for the use of nuclear weapons.
First strike
First strike: The launch of a surprise attack intended to considerably weaken or destroy an adversary's military infrastructure or nuclear forces, and thus severely reduce the adversary’s ability to attack or retaliate.
Warsaw Pact
Warsaw Pact: Created in 1955 by the Soviet Union and its six Central European satellites, this military and political security alliance was the counterpart of NATO. It was formally dissolved on 1 April 1991.
Radiation (Ionizing)
Radiation that has sufficient energy to remove electrons from substances that it passes through, forming ions. May include alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions.
Multiple Independently-targetable Reentry Vehicle (MIRV)
An offensive ballistic missile system with multiple warheads, each of which can strike a separate target and can be launched by a single booster rocket.
Nuclear Posture Review
Under a mandate from the U.S. Congress, the Department of Defense regularly conducts a comprehensive Nuclear Posture Review to set forth the direction of U.S. nuclear weapons policies. To date, the United States has completed four Nuclear Posture Reviews (in 1994, 2001, 2010, and 2018).
Enriched uranium
Enriched uranium: Uranium with an increased concentration of the isotope U-235, relative to natural uranium. Natural uranium contains 0.7 percent U-235, whereas nuclear weapons typically require uranium enriched to very high levels (see the definitions for “highly enriched uranium” and “weapons-grade”). Nuclear power plant fuel typically uses uranium enriched to 3 to 5 percent U-235, material that is not sufficiently enriched to be used for nuclear weapons.
Weapons-grade material
Weapons-grade material: Refers to the nuclear materials that are most suitable for the manufacture of nuclear weapons, e.g., uranium (U) enriched to 90 percent U-235 or plutonium (Pu) that is primarily composed of Pu-239 and contains less than 7% Pu-240. Crude nuclear weapons (i.e., improvised nuclear devices), could be fabricated from lower-grade materials.
Highly enriched uranium (HEU)
Highly enriched uranium (HEU): Refers to uranium with a concentration of more than 20% of the isotope U-235. Achieved via the process of enrichment. See entry for enriched uranium.
Safeguards
Safeguards: A system of accounting, containment, surveillance, and inspections aimed at verifying that states are in compliance with their treaty obligations concerning the supply, manufacture, and use of civil nuclear materials. The term frequently refers to the safeguards systems maintained by the International Atomic Energy Agency (IAEA) in all nuclear facilities in non-nuclear weapon state parties to the NPT. IAEA safeguards aim to detect the diversion of a significant quantity of nuclear material in a timely manner. However, the term can also refer to, for example, a bilateral agreement between a supplier state and an importer state on the use of a certain nuclear technology.

See entries for Full-scope safeguards, information-driven safeguards, Information Circular 66, and Information Circular 153.
International Atomic Energy Agency (IAEA)
IAEA: Founded in 1957 and based in Vienna, Austria, the IAEA is an autonomous international organization in the United Nations system. The Agency’s mandate is the promotion of peaceful uses of nuclear energy, technical assistance in this area, and verification that nuclear materials and technology stay in peaceful use. Article III of the Nuclear Non-Proliferation Treaty (NPT) requires non-nuclear weapon states party to the NPT to accept safeguards administered by the IAEA. The IAEA consists of three principal organs: the General Conference (of member states); the Board of Governors; and the Secretariat. For additional information, see the IAEA.
Safeguards
Safeguards: A system of accounting, containment, surveillance, and inspections aimed at verifying that states are in compliance with their treaty obligations concerning the supply, manufacture, and use of civil nuclear materials. The term frequently refers to the safeguards systems maintained by the International Atomic Energy Agency (IAEA) in all nuclear facilities in non-nuclear weapon state parties to the NPT. IAEA safeguards aim to detect the diversion of a significant quantity of nuclear material in a timely manner. However, the term can also refer to, for example, a bilateral agreement between a supplier state and an importer state on the use of a certain nuclear technology.

See entries for Full-scope safeguards, information-driven safeguards, Information Circular 66, and Information Circular 153.
Dual-use item
An item that has both civilian and military applications. For example, many of the precursor chemicals used in the manufacture of chemical weapons have legitimate civilian industrial uses, such as the production of pesticides or ink for ballpoint pens.
Thermonuclear weapon
Thermonuclear weapon: A nuclear weapon in which the fusion of light nuclei, such as deuterium and tritium, leads to a significantly higher explosive yield than in a regular fission weapon. Thermonuclear weapons are sometimes referred to as staged weapons, because the initial fission reaction (the first stage) creates the condition under which the thermonuclear reaction can occur (the second stage). Also archaically referred to as a hydrogen bomb.
Megaton (MT)
Megaton (MT): The energy equivalent released by 1,000 kilotons (1,000,000 tons) of trinitrotoluene (TNT) explosive. Typically used as the unit of measurement to express the amount of energy released by a nuclear bomb.
Tactical nuclear weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-range missiles, deployed for use in battlefield operations.
Diffusion
Diffusion: A technique for uranium enrichment in which the lighter Uranium 235 isotopes in UF6 gas move through a porous barrier more rapidly than the heavier Uranium 238 isotopes.
Fissile material
Fissile material: A type of fissionable material capable of sustaining a chain reaction by undergoing fission upon the absorption of low-energy (or thermal) neutrons. Uranium-235, Plutonium-239, and Uranium-233 are the most prominently discussed fissile materials for peaceful and nuclear weapons purposes.
Downblending
Downblending: Refers to the process of blending down HEU to LEU. This is done by mixing HEU and the blendstock (of natural, depleted, or slightly enriched uranium) in either liquid or gas form. See highly enriched uranium and low enriched uranium.
Radioactivity
Radioactivity: The spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nucleus of an unstable isotope.
Fallout
The process of the descent to the earth's surface of particles contaminated with radioactive material from a radioactive cloud. The term is also applied in a collective sense to the contaminated particulate matter itself. The early (or local) fallout is defined, somewhat arbitrarily, as those particles which reach the earth within 24 hours after a nuclear explosion. The delayed (or worldwide) fallout consists of the smaller particles which ascend into the upper troposphere and stratosphere, to be carried by winds to all parts of the earth. The delayed fallout is brought to earth, mainly by rain and snow, over extended periods ranging from months to years, and can contaminate the animal food-chain.
Limited Test Ban Treaty
Also known as the Partial Test Ban Treaty, the Treaty Banning Nuclear Weapons Tests in the Atmosphere, in Outer Space and Under Water prohibits nuclear weapons tests "or any other nuclear explosion" in the atmosphere, in outer space, and under water. While the treaty does not ban tests underground, it does prohibit nuclear explosions in this environment if they cause "radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control" the explosions were conducted. The treaty is of unlimited duration. For additional information, see the PTBT.
Entry into force
The moment at which all provisions of a treaty are legally binding on its parties. Every treaty specifies preconditions for its entry into force. For example, the NPT specified that it would enter into force after the United States, the United Kingdom, and the Soviet Union (the Depository governments) and 40 other countries ratified the treaty, an event that occurred on March 5, 1970. See entries for Signature, Ratification.
Zangger Committee (ZC)
A group of 35 nuclear exporting states established in 1971 under the chairmanship of Claude Zangger of Switzerland. The purpose of the committee is to maintain a "trigger list" of: (1) source or special fissionable materials, and (2) equipment or materials especially designed or prepared for the processing, use, or production of special fissionable materials. Additionally, the committee has identified certain dual-use technologies as requiring safeguarding when they are supplied to non-nuclear weapon states. These include explosives, centrifuge components, and special materials. The Zangger Committee is an informal arrangement, and its decisions are not legally binding upon its members. For more information see the Zangger Committee
Nuclear Suppliers Group (NSG)
The NSG was established in 1975, and its members commit themselves to exporting sensitive nuclear technologies only to countries that adhere to strict non-proliferation standards. For additional information, see the NSG.
Export control
National laws or international arrangements established to restrict the sale of certain goods to certain countries, or to ensure that safeguards or end-use guarantees are applied to the export and sale of sensitive and dual-use technologies and materials. See entry for Dual-use
Strategic Arms Limitations Talks (SALT I & II)
Strategic Arms Limitations Talks (SALT I & II): A series of discussions between the Soviet Union and the United States aimed at limiting missile systems and other strategic armaments. The first round of talks (SALT I) was held from 1969 to 1972, and concluded with the 20 May 1971 signing of the Anti-Ballistic Missile (ABM) Treaty and the Interim Agreement limiting strategic offensive arms. SALT II was held from 1972 to 1979. The SALT II Treaty was signed on 18 June 1979, but was not ratified by either country, although both committed to abiding by its limits. For additional information, see the entries for SALT I and SALT II.
Anti-Ballistic Missile (ABM) Treaty
The Anti-Ballistic Missile (ABM) Treaty, which was signed by the United States and the Soviet Union on May 26, 1972, and entered into force on October 3, 1972, constrained strategic missile defenses to a total of 200 launchers and interceptors per country, which were divided between two widely separated deployment areas. These restrictions were intended to prevent the establishment of a nationwide defense, and the creation of a base for deploying such a defense. The treaty was modified in 1974, reducing the permitted deployment areas to one per country. The United States withdrew from the ABM Treaty in 2002. For additional information, see the Anti-Ballistic Missile Treaty.
Deployment
The positioning of military forces – conventional and/or nuclear – in conjunction with military planning.
Silo
Hardened underground facility for housing and launching a ballistic missile.
Comprehensive Nuclear-Test-Ban Treaty (CTBT)
The CTBT: Opened for signature in 1996 at the UN General Assembly, the CTBT prohibits all nuclear testing if it enters into force. The treaty establishes the Comprehensive Test Ban Treaty Organization (CTBTO) to ensure the implementation of its provisions and verify compliance through a global monitoring system upon entry into force. Pending the treaty’s entry into force, the Preparatory Commission of the CTBTO is charged with establishing the International Monitoring System (IMS) and promoting treaty ratifications. CTBT entry into force is contingent on ratification by 44 Annex II states. For additional information, see the CTBT.
Ratification
Ratification: The implementation of the formal process established by a country to legally bind its government to a treaty, such as approval by a parliament. In the United States, treaty ratification requires approval by the president after he or she has received the advice and consent of two-thirds of the Senate. Following ratification, a country submits the requisite legal instrument to the treaty’s depository governments Procedures to ratify a treaty follow its signature.

See entries for Entry into force and Signature.
Intermediate-Range Nuclear Forces (INF) Treaty
A treaty between the United States and the former Soviet Union, signed on 8 December 1987, which entered into force on 1 June 1988. It aimed to eliminate and ban all ground-launched ballistic and cruise missiles with a range of between 300 and 3,400 miles (500 to 5,500 kilometers). The treaty required the United States and the Soviet Union to conduct inspections at each other's sites during the elimination of treaty-limited items (TLI). By May 1991, all intermediate-range and shorter-range missiles, launchers, related support equipment, and support structures were eliminated. For additional information, see the INF Treaty.
Cruise missile
An unmanned self-propelled guided vehicle that sustains flight through aerodynamic lift for most of its flight path. There are subsonic and supersonic cruise missiles currently deployed in conventional and nuclear arsenals, while conventional hypersonic cruise missiles are currently in development. These can be launched from the air, submarines, or the ground. Although they carry smaller payloads, travel at slower speeds, and cover lesser ranges than ballistic missiles, cruise missiles can be programmed to travel along customized flight paths and to evade missile defense systems.
Strategic Arms Reduction Treaty (START I, II, & III)
Refers to negotiations between the United States and the Soviet Union/Russian Federation, held between 1982 and 1993 to limit and reduce the numbers of strategic offensive nuclear weapons in each country’s nuclear arsenal. The talks culminated in the 1991 START I Treaty, which entered into force in December 1994, and the 1993 START II Treaty. Although START II was ratified by the two countries, it never entered into force. In 1997, U.S. President Bill Clinton and Russian President Boris Yeltsin discussed the possibility of a START III treaty to make further weapons reductions, but negotiations resulted in a stalemate. Following the U.S. withdrawal from the Anti-Ballistic Missile Treaty (ABM) in 2002, Russia declared START II void. START I expired on 5 December 2009, and was followed by the New START treaty. See entries for New START and the Trilateral Statement. For additional information, see the entries for START I, START II, and New START
Presidential Nuclear Initiatives (PNI)
PNI: A series of initiatives announced in 1991 by U.S. President George H. W. Bush and Soviet General Secretary Mikhail Gorbachev, declaring that their two countries would reduce tactical nuclear weapons arsenals and associated delivery systems.
Tactical nuclear weapons
Short-range nuclear weapons, such as artillery shells, bombs, and short-range missiles, deployed for use in battlefield operations.
Conference on Disarmament (CD)
The CD is an international forum focused on multilateral disarmament efforts. Although it reports to the UN General Assembly and has a relationship with the United Nations, it adopts its own rules of procedure and agenda, giving it some degree of independence. The CD has a permanent agenda devoted to the negotiation of disarmament issues. The CD and its predecessors have negotiated major nonproliferation and disarmament agreements such as the NPT, the BTWC, the CWC, and the CTBT. In recent years, the CD has focused on negotiating a treaty banning the production of fissile material for nuclear weapons or other nuclear explosive devices; the prevention of an arms race in outer space (PAROS); and negative security assurances. For additional information, see the CD.
United Nations General Assembly
The UN General Assembly is the largest body of the United Nations. It includes all member states, but its resolutions are not legally binding. It is responsible for much of the work of the United Nations, including controlling finances, passing resolutions, and electing non-permanent members of the Security Council. It has two subsidiary bodies dealing particularly with security and disarmament: the UN General Assembly Committee on Disarmament and International Security (First Committee); and the UN Disarmament Commission. For additional information, see the UNGA.
Strategic Offensive Reductions Treaty (SORT)
SORT: Russian President Vladimir Putin and U.S. President George W. Bush signed the Strategic Offensive Reductions Treaty, also called the Treaty of Moscow on 24 May 2002. The treaty stated that both the United States and Russia would reduce the numbers of their deployed nuclear warheads to between 1700 and 2200 within the next ten years. It established a Bilateral Implementation Commission, scheduled to meet at least twice a year, to establish procedures to verify and assist reductions. The treaty was rendered obsolete by the signing of the New START treaty in 2010. For additional information, see SORT.
New START
New START: A treaty between the United States and Russia on further limitations and reductions of strategic offensive weapons, signed on 8 April 2010, which entered into force on 5 February 2011. Under the New START provisions, the two sides have to reduce the number of deployed strategic warheads and the number of deployed strategic delivery vehicles within seven years of the treaty’s entry into force. The treaty’s verification measures are based on the earlier verification system created under START I. New START supersedes the Moscow Treaty, and its duration is 10 years, with an option of extension for up to five years. See entry for Strategic Arms Reduction Treaty and Treaty of Moscow. For additional information, see New START.
Atomic Energy Act of 1954
Atomic Energy Act of 1954: A piece of legislation that governs the development, utilization, and disposal of U.S. nuclear materials and facilities, as well as U.S. nuclear cooperation with other countries. See also the entry for Nuclear Cooperation (Section123) Agreement.
Section 123 Agreement
Section 123 Agreement: See Nuclear Cooperation (Section 123) Agreement.
European Atomic Energy Community (Euratom)
Euratom: Launched in 1958 to facilitate the development of nuclear energy for peaceful purposes within the European Community. For additional information, see EURATOM.

Sources

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  29. Hans M. Kristensen and Robert S. Norris, “US nuclear forces, 2017,” Bulletin of the Atomic Scientists 73, No. 1 (January 2017), p. 51.
  30. Michael A. Miller, “U.S. Air Force Bomber Sustainment and Modernization: Background and Issues for Congress,” Congressional Research Service, 23 April 2013, www.fas.org.
  31. Hans M. Kristensen and Robert S. Norris, “US nuclear forces, 2017,” Bulletin of the Atomic Scientists 73, No. 1 (January 2017), p. 52.
  32. Hans M. Kristensen and Robert S. Norris, “US nuclear forces, 2017,” Bulletin of the Atomic Scientists 73, No. 1 (January 2017), p. 52-53.
  33. Hans M. Kristensen and Robert S. Norris, “US nuclear forces, 2017,” Bulletin of the Atomic Scientists 73, No. 1 (January 2017), p. 52.
  34. U.S. Department of Energy, “Fiscal Year 2014 Stockpile Stewardship and Management Plan,” June 2013, p. 10-18.
  35. U.S. Department of Energy, “Fiscal Year 2017 Stockpile Stewardship and Management Plan,” March 2016, pp. 1-7.
  36. Congressional Budget Office, “Projected Costs of U.S. Nuclear Forces, 2017 to 2026,” Congress of the United States, February 2017, p. 1.
  37. “Projected Costs of U.S. Nuclear Forces, 2017 to 2026,” Congressional Budget Office, February 2017, www.cbo.gov.
  38. Kingston Reif, “U.S.-Russia Nuclear Forces and Arms Control Agreements,” Arms Control Association, 7 June 2017, www.armscontrol.org. Sources: Navy, Air Force, CSIS, NNSA, DoD Cost Assessment and Program Evaluation Office.
  39. Kingston Reif, “U.S.-Russia Nuclear Forces and Arms Control Agreements,” Arms Control Association, 7 June 2017, www.armscontrol.org. Sources: Navy, Air Force, CSIS, NNSA, DoD Cost Assessment and Program Evaluation Office.
  40. Congressional Budget Office, “Projected Costs of U.S. Nuclear Forces, 2017 to 2026,” Congress of the United States, February 2017, p. 1; Jon B. Wolfsthal, Jeffrey Lewis, and Marc Quint, The Trillion Dollar Nuclear Triad: U.S. Strategic Modernization over the Next Thirty Years, (Monterey: James Martin Center for Nonproliferation Studies, January 2014), p. 8-9.
  41. Willian J. Broad & David E. Sanger, “U.S. Ramping Up Major Renewal in Nuclear Arms,” New York Times, 28 September 2014, www.nytimes.com.
  42. Patrick Malone, “Trump seeks to spend more on nuclear weapons by buys little added capability,” The Center for Public Integrity, 26 May 2017, www.publicintegrity.org.
  43. This section draws upon the following sources: David Alan Rosenberg, “The Origins of Overkill: Nuclear Weapons and American Strategy, 1945-1960,” International Security 7 (Spring 1983), pp. 3-71; David Alan Rosenberg, “Nuclear War Planning,” in The Laws of War: Constraints on Warfare in the Western World, Michael Howard, et al., eds. (New Haven: Yale University Press, 1994); Freedman, The Evolution of Nuclear Strategy, 3rd ed. (New York: Palgrave Macmillan, 2003); Scott D. Sagan, Moving Targets: Nuclear Strategy and National Security (Princeton, NJ: Princeton University Press, 1989), esp. pp. 10-57; Lynn Eden, Whole World on Fire: Organizations, Knowledge & Nuclear Weapons Devastation (Ithaca, NY: Cornell University Press, 2006).
  44. National Security Archive, “First Declassification of Eisenhower’s Instructions to Commanders Predelegating Nuclear Weapons Use, 1959-60,” 18 May 2001, www2.gwu.edu.
  45. Lynn Eden, Whole World on Fire: Organizations, Knowledge & Nuclear Weapons Devastation (Ithaca, NY: Cornell University Press, 2006).
  46. The White House: Office of the Press Secretary, “Fact Sheet: Nuclear Weapons Employment Strategy of the United States,” 19 June 2013, www.whitehouse.gov.
  47. White House, “Fact Sheet: Nuclear Weapons Employment Strategy of the United States,” 19 June 2013, www.whitehouse.gov.
  48. Steve Herman, “Trump Administration Reviewing What Role US Nuclear Weapons Should Play,” VOA News, 27 March 2017, www.voanews.com.
  49. $2 billion in 1942 has the equivalent purchasing power of roughly $28.5 billion in 2013. See Joseph Cirincione, Bomb Scare: The History & Future of Nuclear Weapons (New York, NY: Columbia University Press, 2007), p. 7.
  50. See, for example, Denise Kiernan, The Girls of Atomic City: The Untold Story of the Women Who Helped Win World War II (New York, NY: Simon & Shuster, 2013).
  51. Dwight D. Eisenhower, “Address by Mr. Dwight D. Eisenhower, President of the United States of America, to the 470th Plenary Meeting of the United Nations General Assembly,” 8 December 1953, www.iaea.org.
  52. Barton J. Bernstein, “Truman and the H-Bomb,” Bulletin of the Atomic Scientists 40 (March, 1984), p. 13.
  53. Joseph Cirincione, Bomb Scare: The History & Future of Nuclear Weapons (New York, NY: Columbia University Press, 2007), p. 21.
  54. Joseph Cirincione, Bomb Scare: The History & Future of Nuclear Weapons (New York, NY: Columbia University Press, 2007), p. 23, “the Soviets tested its first fusion device…on 12 August 1953…” Bravo was “the first deliverable H-bomb… and the Soviets dropped their first true H-bomb on 23 November 1955.”
  55. Stephen I. Schwartz, “Introduction,” in Stephen I. Schwarz, ed., Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940 (Washington, DC: Brookings Institution Press, 1998), pp. 18-21.
  56. Robert S. Norris and Stephen I. Schwartz, “Growth and Evolution of the U.S. Nuclear Stockpile,” in Schwarz, ed., Atomic Audit, pp. 44-45, www.brookings.edu.
  57. “U.S. Nuclear Weapons Reduction,” AtomicBombMuseum.org, 2006; for a detailed listing of stockpile numbers by year (1962-2009), see “Fact Sheet: Increasing Transparency in the U.S. Nuclear Weapons Stockpile,” 3 May 2010, www.defense.gov.
  58. Robert S. Norris, William M. Arkin, and William Burr, “Where They Were,” Bulletin of the Atomic Scientists 55 (November/December 1999), p. 26.
  59. “Countries: United States,” International Panel on Fissile Materials, Updated 5 August 2016, http://fissilematerials.org.
  60. For a comprehensive table listing all of the US nuclear tests by date, see: www.fas.org.
  61. International Physicians for the Prevention of Nuclear War and the Institute for Energy and Environmental Research, Radioactive Heaven and Earth: The Health and Environmental Effects of Nuclear Weapons Testing in, on, and above the Earth (New York: Apex Press, 1991), pp. 50-56.
  62. India, Pakistan, and Israel remain the only three states never to have signed the NPT. The Democratic People’s Republic of Korea (North Korea) announced its withdrawal in 2003, but its withdrawal has not been formally recognized by the NPT regime. See, for example, George Bunn and Christopher F. Chyba, U.S. Nuclear Weapons Policy: Confronting Today’s Threats (Washington: Brookings Institution Press, 2006), p. 124.
  63. For a list of Zangger Committee members, as well as a list of the Zangger “Trigger List”, see: www.zanggercommittee.org; for an updated list of NSG members, see “The Nuclear Suppliers Group (NSG) at a Glance,” Arms Control Association, October 2012, www.armscontrol.org.
  64. Nuclear Threat Initiative, “Strategic Arms Limitation Talks (SALT I),” www.nti.org.
  65. Eli Corin, “Presidential Nuclear Initiatives: An Alternative Paradigm for Arms Control,” Nuclear Threat Initiative, 1 March 2004, www.nti.org.
  66. The CTBT requires the ratification of a specified list of 44 nuclear capable states stipulated in the second annex. For a current list of ratifications, including those by Annex 2 states, see www.ctbto.org.
  67. See Andrew Futter and Benjamin Zala, “Advanced US Conventional Weapons and Nuclear Disarmament: Why the Obama Plan Won’t Work,” Nonproliferation Review 20 (March 2013), pp. 107-22; and Nikolai Sokov, “Assessing Russian Attitudes Toward Phased, Deep Nuclear Reductions: Strategic and Regional Aspects,” Nonproliferation Review 20 (July 2013), pp. 247-61.
  68. Jonathan Landay and David Rohde, “Exclusive: In call with Putin, Trump denounced Obama-era nuclear arms treaty-sources,” Reuters, 9 February 2017, www.reuters.com.
  69. “National Defense Authorization Act for Fiscal Year 2018,” Senate Armed Services Committee, www.armed-services.senate.gov.; “H.R. 2810-FY18 National Defense Authorization Bill: Chairman’s Mark,” House Armed Services Committee, www.armedservices.house.gov.
  70. U.S. Energy Information Administration, “Frequently Asked Questions: How many nuclear power plants are in the United States, and where are they located?” 30 May 2017, www.eia.gov.
  71. U.S. Energy Information Administration, “Frequently Asked Questions: How many nuclear power plants are in the United States, and where are they located?” 30 May 2017, www.eia.gov; Tom Hals, “Westinghouse reaches deal for $800 million U.S. bankruptcy loan,” Reuters, 23 May 2017, www.reuters.com.
  72. Tom Hals, “Westinghouse reaches deal for $800 million U.S. bankruptcy loan,” Reuters, May 23, 2017, www.reuters.com.
  73. See, for example, Charles D. Ferguson and Frank A. Settle, eds., “The Future of Nuclear Power in the United States,” Federation of American Scientists/Washington and Lee University, February 2012, www.fas.org.
  74. “The U.S. Atomic Energy Act Section 123 At a Glance,” Arms Control Association, updated March 2013, www.armscontrol.org.
  75. “123 Agreements for Peaceful Cooperation,” National Nuclear Security Administration, January 20, 2017, www.nnsa.energy.gov.

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