Contacts: Daryl Kimball, Executive Director; (202) 463-8270 x107; Kelsey Davenport, Director of Nonproliferation Policy, (202) 463-8270 x102; Kingston Reif, Director of Disarmament and Threat Reduction Policy, (202) 463-8270 x104
Updated: March 2018
The 2018 Nuclear Posture Review repeats exisiting U.S. negative security assurances by stating that Washington "will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the NPT and in compliance with their nuclear non-proliferation obligations." Previously, in the April 2010 Nuclear Posture Review (NPR), the United States declared that it would not use nuclear weapons against non-nuclear-weapon states that are members in good standing of the nuclear Nonproliferation Treaty (NPT). Before 2010 successive administrations had maintained a policy of "strategic ambiguity" by refusing to rule out the use of nuclear weapons in response to biological or chemical weapons attacks, even from NPT member states.
The 2018 NPR upholds but adds qualifications to earlier versions of U.S. "negative security assurances" first enunciated in 1978 and reaffirmed in 1995. Most notably, the report stipulates that the United States reserves the right to amend its negative assurance if warranted by "the evolution and proliferation of non-nuclear strategic attack technologies," including cyber capabilites.
The 1995 formulation left open the option to use or threaten to use nuclear weapons against non-nuclear-weapon states that were “in association or alliance with” a nuclear-weapon state—generally understood to be a reference to the Warsaw Pact allies of the Soviet Union. The United States also specified at that time that non-nuclear-weapon states had to be in compliance with the NPT to be eligible for this assurance.
In 1995, UN Security Council Resolution 984 recognized the U.S. assurances and similar ones from Russia, China, France and the United Kingdom. These coordinated assurances were a key part of the multilateral decision to indefinitely extend the NPT that year.
Outside of the NPT context, however, senior U.S. officials maintained "strategic ambiguity" about Washington’s military options in key situations. For example, just before the U.S. war with Iraq in 1991, former Secretary of State James Baker told Tariq Aziz, Iraq's foreign minister, that if "you use chemical or biological weapons against U.S. forces, the American people will demand vengeance and we have the means to exact it." Baker said that "it is entirely possible and even likely, in my opinion, that Iraq did not use its chemical weapons against our forces because of that warning. Of course, that warning was broad enough to include the use of all types of weapons that American possessed."
Similarly, in April 1996, in reference to a suspected Libyan chemical weapons facility at Tarhunah, then-Secretary of Defense William Perry said that "if some nation were to attack the United States with chemical weapons, then they would have to fear the consequences of a response from any weapon in our inventory." Perry noted that "in every situation that I have seen so far, nuclear weapons would not be required for response."
The 2001 NPR report maintained the possibility that U.S. nuclear forces could be used against non-nuclear nations. In addition to nuclear-armed China, the 2001 NPR cited five states that at the time did not have nuclear weapons (Iran, Iraq, Libya, North Korea and Syria) as driving "requirements for nuclear strike capabilities." All five states were at the time suspected of nuclear weapons ambitions and were believed to have biological and/or chemical weapons or programs. In February 2002, then-State Department spokesman Richard Boucher said it was U.S. policy that "[i]f a weapon of mass destruction is used against the United States or its allies, we will not rule out any specific type of military response."
In September 2002, the classified National Security Presidential Directive 17 was signed, which stated that "the United States will continue to make clear that it reserves the right to respond with overwhelming force—including potentially nuclear weapons — to the use of WMD against the United States, our forces abroad, and friends and allies."
Following the release of the 2010 Nuclear Posture Review report, President Barack Obama announced on April 6, that the
As Secretary of Defense Robert Gates explained in an interview broadcast April 11, 2010 on CBS’s Face the Nation, negative security assurances are “not a new thing. The new part of this is saying that we would not use nuclear weapons against a non-nuclear state that attacked us with chemical and biological weapons.”
As for chemical weapons, Gates said April 11 that “[T]ry as we might, we could not find a credible scenario where a chemical weapon could have the kind of consequences that would warrant a nuclear response.” On biological weapons, the 2010 NPR hedges: “Given the catastrophic potential of biological weapons and the rapid pace of bio-technology development, the United States reserves the right to make any adjustment in the assurance that may be warranted by the evolution and proliferation of the biological weapons threat and U.S. capacities to counter that threat.”
For both scenarios, Gates said April 6 that “[i]f any state eligible for this assurance were to use chemical or biological weapons against the United States or its allies or partners, it would face the prospect of a devastating conventional military response.” And for states that have nuclear weapons or are not in compliance with the NPT all options are on the table—including the use of nuclear weapons first or in response to a non-nuclear attack.
Under the NPT, the five recognized nuclear-weapon states are China, France, Russia, the United Kingdom, and the United States. Three other states, India, Pakistan, and Israel, possess nuclear weapons but never joined the NPT.
Although the 2018 NPR report makes clear that the primary role of U.S. nuclear weapons is to “deter nuclear attack on the United States, our allies, and partners,” the weapons serve other missions, too, including deterring non-nuclear attacks, assuring U.S. allies and partners, achieving U.S. objectives if deterrence fails, and hedging against future uncertainty. This falls short of a declaration that the “sole purpose” of U.S. nuclear weapons is to deter nuclear attack and represents a significant break with past U.S. efforts to reduce the role and number of nuclear weapons in the world.
The 2018 NPR report does state that the first use of nuclear weapons will only be considered under “extreme circumstances,” but it defines these circumstances more broadly than previous reports, including in the definition “significant non-nuclear strategic attacks” against “U.S., allied or partner civilian population or infrastructure, and attacks on U.S. or allied nuclear forces, their command and control, or warning and attack assessment capabilities.” Although the policy does not explicitly define “significant non-nuclear strategic attacks,” Undersecretary of Defense for Policy John Rood clarified at the February 2 press conference following the report’s release that this could include chemical and biological attacks, large-scale conventional aggression, and cyberattacks. The scenarios provided for in the 2018 NPR report are much broader than the “narrow range of contingencies” laid out in the 2010 report.
The document also breaks from the 2010 report on the role of non-nuclear forces. Whereas the 2010 report called for enhanced non-nuclear capability to maintain deterrence, the 2018 document states that “non-nuclear capabilities can complement but not replace U.S. nuclear capabilities” for the purpose of deterrence. Moreover, if deterrence fails, the 2018 report also declares that Washington may use nuclear weapons to end a conflict on the “best achievable terms for the United States.”