On January 30, 2019, Senator Elizabeth Warren and Representative Adam Smith introduced legislation (S. 272/H.R. 921) that declared, "It is the policy of the United States to not use nuclear weapons first." Other Members of Congress are divided on this issue. Senator Dianne Feinstein has argued that the only moral use for U.S. nuclear weapons is as a deterrent to their use. Senator Deb Fischer, on the other hand, has said that the proposal "betrays a naïve and disturbed world view."
A "no first use" policy would represent a change from current policy, where the United States has pledged to refrain from using nuclear weapons against most non-nuclear weapon states, but has neither ruled out their first use in all cases nor specified the circumstances under which it would use them. This policy of "calculated ambiguity" addressed U.S. concerns during the Cold War, when the United States and NATO faced numerically superior Soviet and Warsaw Pact conventional forces in Europe. At the time, the United States not only developed plans to use nuclear weapons on the battlefield to disrupt or defeat attacking tanks and troops, but it also hoped that the risk of a nuclear response would deter the Soviet Union from initiating a conventional attack. This is not because the United States believed it could defeat the Soviet Union in a nuclear war, but because it hoped the Soviet Union would know that the use of these weapons would likely escalate to all-out nuclear war, with both sides suffering massive destruction.
Since the end of the Cold War, the United States has modified its declaratory policy to reduce the apparent role of nuclear weapons in U.S. national security, but it still has not declared that it would not use them first. In the 2010 Nuclear Posture Review Report, the Obama Administration stated that the United States "would only consider the use of nuclear weapons in extreme circumstances" and would not threaten or use nuclear weapons, under any circumstances, "against non-nuclear weapons states that are party to the Nuclear Nonproliferation Treaty and in compliance with their nuclear non-proliferation obligations." But the Administration was not prepared to state that the "sole purpose" of U.S. nuclear weapons was to deter nuclear attack because it could envision "a narrow range of contingencies" where nuclear weapons might play a role in deterring conventional, chemical, or biological attacks.
The Trump Administration, in the 2018 Nuclear Posture Review (NPR) Report, also rejected the idea that the sole purpose of nuclear weapons is to deter nuclear attack, and, therefore, also did not adopt a "no first use" policy. It noted that "the United States would only consider the employment of nuclear weapons in extreme circumstances to defend the vital interests of the United States, its allies, and partners" but stated that nuclear weapons contribute to "deterrence of nuclear and non-nuclear attack; assurance of allies and partners; achievement of U.S. objectives if deterrence fails; and the capacity to hedge against an uncertain future."
Although the United States does not rule out the first use of nuclear weapons, the absence of a "no first use" pledge is less about the perceived need to employ these weapons first in a conflict than it is about the view that the threat of nuclear escalation continues to serve as a deterrent to large-scale conventional war or the use of chemical and biological weapons. Supporters of the current policy argue that removing the threat of nuclear escalation could embolden countries like North Korea, China, or Russia, who might believe that they could overwhelm U.S. allies in their regions and take advantage of local or regional conventional advantages before the United States or its allies could respond. In such a scenario, some argue, the "no first use" pledge would not only undermine deterrence, but could also increase the risk that a conventional war could escalate and involve nuclear weapons use. Moreover, because the United States has pledged to use all means necessary, including nuclear weapons, to defend allies in Europe and Asia, this change in U.S. declaratory policy could undermine allies' confidence in the U.S. commitment to their defense and possibly spur them to acquire their own nuclear weapons. As a result, in this view, a "no first use" policy could undermine U.S. nuclear nonproliferation goals.
Some analysts outside government dispute these conclusions. Some assert a lack of evidence that the threat of nuclear escalation can deter conventional war, while others note that U.S. nuclear first-use might spark a nuclear response and an all-out nuclear exchange. Moreover, some contend that a "no first use" policy would not undermine the U.S. commitment to its allies because those states have faith in U.S. conventional forces for their defense, as well as knowledge of the U.S. willingness to retaliate with nuclear weapons in response to nuclear attacks. Others, including Senator Warren and Representative Smith, note that a "no first use" pledge could reduce the chances of nuclear miscalculation by assuring adversaries that the United States was not about to launch a preemptive nuclear attack. Hence, many conclude that the possible first use of nuclear weapons is not only unnecessary, but also might turn conventional war into a nuclear catastrophe.
Press reports indicate that the Obama Administration considered adopting a "no first use" policy in 2016. However, these reports indicate that both military and civilian officials opposed this change. Air Force officials argued that a policy of calculated ambiguity provided the President with options in a crisis. Admiral Haney, then the Commander in Chief of Strategic Command, noted that the shift could undermine deterrence and stability in an uncertain security environment. Secretary of State Kerry and Secretary of Defense Carter also raised concerns that a "no first use" policy could undermine the confidence and security of U.S. allies. Secretary of Energy Moniz also expressed opposition. Reports indicate that several allies also weighed in against the change in policy.