Contact: Daryl Kimball, executive director
Over the past five decades, U.S. and Soviet/Russian leaders have used a progression of bilateral agreements and other measures to limit and reduce their substantial nuclear warhead and strategic missile and bomber arsenals. The following is a brief summary.
Strategic Nuclear Arms Control Agreements
Begun in November 1969, the Strategic Arms Limitation Talks (SALT) produced two agreements by May 1972.
The Anti-Ballistic Missile (ABM) Treaty limited strategic missile defenses to 200 (later 100) interceptors each. In June 2002, the United States unilaterally withdrew from the ABM Treaty, feeling that it limited the country’s ability to defend itself against terrorist or “rogue-state” ballistic missile attacks.
Under the second negotiated deal, the Interim Agreement, both sides pledged not to construct new ICBM silos and not to increase the dimensions of existing ICBM silos “significantly,” as well as capped the number of SLBM launch tubes and SLBM-carrying submarines. The agreement ignored strategic bombers and did not address warhead numbers but succeeded in limiting the United States to 1,054 ICBM silos and the Soviet Union to 1,618 ICBM silos. The agreement also capped the number of SLBM launch tubes for each side and allowed for an increase in launchers if done alongside the dismantling or destruction of a corresponding number of older ICBM or SLBM launchers. The United States was limited to 710 SLBM launch tubes, from its base level of 656 SLBM launch tubes, and no more than 44 modern ballistic missile submarines. The Soviet Union was limited to 950 SLBM launch tubes, from its base level of 740 SLBM launch tubes, and no more than 62 modern ballistic missile submarines.
In November 1972, Washington and Moscow agreed to pursue a follow-on treaty to SALT I.
Signed in June 1979, SALT II would have limited U.S. and Soviet ICBM, SLBM, and strategic bomber-based nuclear forces to 2,250 delivery vehicles (defined as an ICBM silo, a SLBM launch tube, or a heavy bomber) and placed a variety of other restrictions on deployed strategic nuclear forces. The agreement would have required the Soviets to reduce their forces by roughly 270 delivery vehicles, but U.S. forces were below the limits and could actually have been increased.
U.S. President Jimmy Carter asked the Senate not to consider SALT II for its advice and consent after the Soviet Union invaded Afghanistan in December 1979, and the treaty was not taken up again. Both Washington and Moscow subsequently pledged to adhere to the agreement’s terms despite its failure to enter into force. However, U.S. President Ronald Reagan said on May 26, 1986 that future decisions on strategic nuclear forces would be based on the threat posed by Soviet forces and not on "a flawed SALT II Treaty.”
The Strategic Arms Reduction Treaty (START I), first proposed in the early 1980s by President Ronald Reagan and finally signed in July 1991, required the United States and the Soviet Union to reduce their deployed strategic arsenals to 1,600 delivery vehicles, carrying no more than 6,000 warheads as counted using the agreement’s rules.
The agreement required the destruction of excess delivery vehicles, which was verified using an intrusive verification regime that involved on-site inspections, the regular exchange of information (including telemetry), and the use of national technical means (i.e., satellites). The agreement’s entry into force was delayed for several years because of the collapse of the Soviet Union and the ensuing efforts to denuclearize Ukraine, Kazakhstan, and Belarus by returning their nuclear weapons to Russia and making them parties to the nuclear Nonproliferation Treaty (NPT) and START I agreements.
START I reductions were completed in December 2001, and the treaty expired on Dec. 5, 2009.
In June 1992, Presidents George H. W. Bush and Boris Yeltsin agreed to pursue a follow-on accord to START I.
START II, signed in January 1993, called for ultimately reducing deployed strategic arsenals to 3,000-3,500 warheads and banned the deployment of destabilizing multiple-warhead land-based missiles. START II would have counted warheads in roughly the same fashion as START I and, also like its predecessor, would have required the destruction of delivery vehicles but not warheads.
The agreement's original implementation deadline was January 2003, ten years after signature, but a 1997 protocol moved this deadline to December 2007 because of the extended delay in ratification. Both the Senate and the Duma approved START II, but the treaty did not take effect because the Senate did not ratify the 1997 protocol and several ABM Treaty amendments, whose passage the Duma established as a condition for START II’s entry into force. START II was effectively shelved as a result of the 2002 U.S. withdrawal from the ABM treaty.
START III Framework
In March 1997, Presidents Bill Clinton and Boris Yeltsin agreed to a framework for START III negotiations that included a reduction in deployed strategic warheads to 2,000-2,500.
Significantly, in addition to requiring the destruction of delivery vehicles, START III negotiations were to address “the destruction of strategic nuclear warheads” so as to promote the irreversibility of deep reductions. Negotiations were supposed to begin after START II entered into force, which never happened.
SORT (Moscow Treaty)
On May 24, 2002, Presidents George W. Bush and Vladimir Putin signed the Strategic Offensive Reductions Treaty (SORT or Moscow Treaty) under which the United States and Russia reduced their deployed strategic arsenals to 1,700-2,200 warheads each. The warhead limit took effect and expired on the same day, Dec. 31, 2012. As part of the agreement, the two countries also agreed to keep START I in force, which helped provide the monitoring and verification procedures left out of SORT.
Although the two sides did not agree on specific counting rules, the Bush administration asserted that the United States would reduce only warheads deployed on strategic delivery vehicles in active service (i.e., “operationally deployed” warheads) and would not count warheads removed from service and placed in storage or warheads on delivery vehicles undergoing overhaul or repair. The agreement’s limits are similar to those envisioned for START III, but the treaty did not require the destruction of delivery vehicles, as START I and II did, or the destruction of warheads, as had been envisioned for START III.
The treaty was approved by the Senate and Duma and entered into force on June 1, 2003. SORT was replaced by New START on Feb. 5, 2011.
On April 8, 2010, the United States and Russia signed the New Strategic Arms Reduction Treaty (New START), a legally binding, verifiable agreement limiting each side to 1,550 strategic nuclear warheads deployed on 700 strategic delivery systems (ICBMs, SLBMs, and heavy bombers assigned to a nuclear mission) and limiting deployed and nondeployed launchers, including those in overhaul, to 800. The treaty does not limit non-deployed ICBMs and SLBMs.
The treaty-accountable warhead limit is 30 percent lower than the 2,200 upper limit of SORT, and the delivery vehicle limit is 50 percent lower than the 1,600 allowed in START I. The treaty has a verification regime that combines elements of START I with new elements tailored to New START. Measures under the treaty include on-site inspections and exhibitions, data exchanges and notifications related to strategic offensive arms and facilities covered by the treaty, and provisions to facilitate the use of national technical means for treaty monitoring. The treaty also provides for the continued exchange of telemetry (missile flight-test data on up to five tests per side, per year) and does not meaningfully limit missile defenses or long-range conventional strike capabilities.
The U.S. Senate approved New START on Dec. 22, 2010. The approval process of the Russian parliament (passage by both the State Duma and Federation Council) was completed Jan. 26, 2011. The treaty entered into force on Feb. 5, 2011, and both parties met the treaty’s central limits by the implementation deadline on Feb. 5, 2018. The United States and Russia agreed on Feb. 3, 2021, to extend New START by five years, as allowed by the treaty text, until Feb. 5, 2026.
Strategic Nuclear Arms Control Agreements
Strategic Nuclear Arms Control Agreements
|SALT I||SALT II||INF Treaty||START I||START II||START III||SORT||
|Status||Expired||Never Entered Into Force||Terminated||Expired||Never Entered Into Force||Never Negotiated||Replaced by New START||In Force|
|Deployed Warhead Limit||N/A||N/A||N/A||6,000||3,000-3,500||2,000-2,500||1,700-2,200||1,550|
|Deployed Delivery Vehicle Limit||US: 1,764 ICBMs & SLBMs
|2,250||Prohibits ground-based missiles of 500-5,500 km range||1,600||N/A||N/A||N/A||700|
|Date Signed||May 26, 1972||June 18, 1979||Dec. 8, 1987||July 31, 1991||Jan. 3, 1993||N/A||May 24, 2002||April 8, 2010|
|Date Ratified, U.S.||Aug. 3, 1972||N/A||May 28, 1988||Oct. 1, 1992||Jan. 26, 1996||N/A||March 6, 2003||Dec. 22, 2010|
|Ratification Vote, U.S.||88-2||N/A||93-6||93-6||87-4||N/A||95-0||71-26|
|Date Entered Into Force||Oct. 3, 1972||N/A||June 1, 1988||Dec. 5, 1994||N/A||N/A||June 1, 2003||Feb. 5, 2011|
|Implementation Deadline||N/A||N/A||June 1, 1991||Dec. 5, 2001||N/A||N/A||N/A||Feb. 5, 2018|
|Expiration Date||Oct. 3, 1977||N/A||Aug. 2, 2019||Dec. 5, 2009||N/A||N/A||Feb. 5, 2011||Feb. 5, 2026*|
*Initially set to expire Feb. 5, 2021, New START was extended by five years until 2026 as allowed by the treaty text.
Non-strategic Nuclear Arms Control Measures
Signed Dec. 8, 1987, the Intermediate-Range Nuclear Forces (INF) Treaty required the United States and the Soviet Union to verifiably eliminate all ground-launched ballistic and cruise missiles with ranges between 500 and 5,500 kilometers. Distinguished by its unprecedented, intrusive inspection regime, including on-site inspections, the INF Treaty laid the groundwork for verification of the subsequent START I. The INF Treaty entered into force June 1, 1988, and the two sides completed their reductions by June 1, 1991, destroying a total of 2,692 missiles. The agreement was multilateralized after the breakup of the Soviet Union, and active participants in the agreement came to include the United States, Russia, Belarus, Kazakhstan, and Ukraine. Turkmenistan and Uzbekistan were also parties to the agreement but did not participate in treaty meetings or on-site inspections with permission from the other states-parties. The ban on intermediate-range missiles was of unlimited duration.
Both the United States and Russia raised concerns about the other side’s compliance with the INF Treaty. The United States first publicly charged Russia in 2014 with developing and testing a ground-launched cruise missile—the 9M729 missile—with a range that exceeds the INF Treaty limits.
Russia denied that it breached the agreement and raised its own concerns about Washington’s compliance. Moscow charged that the United States placed a missile defense launch system in Europe that could also be used to fire interceptor and cruise missiles, using targets for missile defense tests with similar characteristics to INF Treaty-prohibited intermediate-range missiles, and was making armed drones that were equivalent to ground-launched cruise missiles.
On Oct. 20, 2018, President Donald Trump announced his intention to “terminate” the agreement citing Russian noncompliance and concerns about China’s missiles, and on Dec. 4, Secretary of State Mike Pompeo declared Russia in “material breach” of the treaty. The Trump administration provided official notice to the other treaty states-parties on Feb. 2, 2019, that it would both suspend its obligations to the treaty and withdraw from the agreement in six months—per the treaty's terms—and "terminate" the agreement unless Russia returned to compliance by eliminating its ground-launched 9M729 missiles.
On Aug. 2, 2019, the United States formally withdrew from the INF Treaty.
On Sept. 27, 1991, President George H.W. Bush announced that the United States would remove almost all U.S. tactical (non-strategic) nuclear forces from deployment so that Russia could undertake similar actions, reducing the risk of nuclear proliferation as the Soviet Union dissolved. Specifically, Bush said the United States would eliminate all of its nuclear artillery shells and short-range ballistic missiles and remove all non-strategic nuclear warheads from surface ships, attack submarines, and land-based naval aircraft.
Soviet leader Mikhail Gorbachev reciprocated on Oct. 5, pledging to eliminate all nuclear artillery munitions, nuclear warheads for tactical missiles, and nuclear landmines. He also pledged to withdraw all Soviet tactical naval nuclear weapons from deployment.
Under these initiatives, the United States and Russia reduced their deployed non-strategic stockpiles by an estimated 5,000 and 13,000 warheads, respectively. However, significant questions remain about Russian implementation of its pledges, and there is considerable uncertainty about the current state of Russia’s tactical nuclear forces. The Defense Department estimates that Russia possesses roughly 1,900 non-strategic nuclear weapons and that the numbers are expanding. The United States maintains an estimated 200 non-strategic B61 gravity bombs.