The Nuclear Posture Review is a legislative-mandated review undertaken by the Department of Defense that outlines U.S. nuclear policy, strategy, capabilities and force posture for the next five to 10 years. Below is a summary of key takeaways from the 2018 document, which can be read in full here.
1. Low-Yield Nuclear Weapons
The review calls for low-yield nuclear weapons, also known as tactical nuclear weapons, as a “flexible” nuclear option.
Explosive yield of a nuclear weapon is the amount of energy released upon detonation; “low yield” qualifies as one to 20 kilotons of energy. (To put this in context, the Hiroshima detonation had a 15- kiloton yield and is considered low-yield.) Although the U.S. nuclear arsenal is mostly composed of warheads with multi-hundred-kiloton yields, it also contains approximately 500 weapons that can be configured for low-yield options.
In the near term, the review calls for modification to “a small number of existing submarine-launched ballistic missile (SLBM) warheads” to provide a low-yield option.
It also calls for further exploration of low-yield options, arguing that expanding these options will “help ensure that potential adversaries perceive no possible advantage in limited nuclear escalation, making nuclear employment less likely.” This is intended to address the argument that adversaries might think the United States, out of concern for collateral damage, would hesitate to employ a high-yield nuclear weapon in response to a “lower level” conflict, in which an adversary used a low-yield nuclear device. The review argues that expanding low-yield options is “important for the preservation of credible deterrence,” especially when it comes to smaller-scale regional conflicts.
While the review makes a point of describing Russia’s flexible nuclear arsenal, including low-yield weapons, it says that expanding the U.S. low-yield capabilities is not an effort to “match or mimic” Russia’s arsenal but, rather, to “counter any mistaken perception of an exploitable ‘gap’ in U.S. regional deterrence capabilities.”
2. Threshold for Employing Nuclear Weapons
While the document strives to maintain “some ambiguity regarding the precise circumstances that might lead to a U.S. nuclear response,” it explicitly states that the United States could employ nuclear weapons in response to “significant non-nuclear strategic attacks.” This includes but is not limited to “attacks on U.S., allied, or partner civilian population or infrastructure.”
Other cases in which the United States could employ nuclear weapons include “attacks on U.S. or allied nuclear forces, their command and control, or warning and attack assessment capabilities.” Thus, the review rejects a “sole purpose” policy, whereby nuclear weapons would be used to deter only nuclear attacks.
The 2018 assessment explicitly rejects a “no first use policy,” whereby nuclear weapons would be used only in retaliation to a nuclear strike, arguing that the United States never adopted such a policy in the past and that “such a policy is not justified today.” The review asserts that the United States would consider deploying nuclear weapons only “in extreme circumstances to defend the vital interests of the United States, its allies and partners,” such as in the situations described above.
3. New Sea-Launched Cruise Missiles
In its long-term assessment, the document calls for development of a “modern” nuclear-armed sea-launched cruise missile.
This marks a departure from the Obama administration’s 2010 Nuclear Posture Review, which announced the retirement of the previous nuclear-armed sea-launched cruise missile.
The 2018 review argues that nuclear-armed cruise missiles launched at sea would provide additional flexibility and diversity in nuclear response options and that U.S. pursuit of such weapons may serve as an “incentive” for Russia to “negotiate seriously a reduction of its non-strategic nuclear weapons.” This is an apparent response to Russia’s alleged violations of the Intermediate-Range Nuclear Forces Treaty, which requires the United States and Russia to eliminate and permanently forswear their nuclear and conventional ground-launched ballistic and cruise missiles with ranges of 500 to 5,500 kilometers, or about 300 to 3,400 miles.
The review promises to “immediately begin efforts to restore this capability” by initiating a capability study on rapid development. “[L]everaging existing technologies” for such a missile will “help ensure its cost effectiveness.”
No exact cost estimate is provided for development. The review provides an approximation of the combined cost of sustaining and replacing all U.S. nuclear capabilities, arguing that while cost estimates for individual programs vary, “even the highest of these projections” place the future cost of the entire U.S. nuclear program at 6.4 percent of the current Department of Defense budget. For context, the review states that the U.S. nuclear program requires 2 to 3 percent of the defense budget. No other estimated figures are provided in the report.
4. U.S. Position Toward International Treaties
The review states that the United States will not seek ratification of the Comprehensive Nuclear Test Ban Treaty.[xvii] That treaty, already ratified by Russia, prohibits nuclear explosions in all environments. The review reaffirms support for the test monitoring undertaken by the treaty’s preparatory committee, andy it states that the United States will not resume nuclear testing unless necessary to ensure the safety and effectiveness of its nuclear arsenal. It also calls on all states possessing nuclear weapons to declare or maintain a moratorium on nuclear testing. Seven other countries with nuclear weapons, including China, have not yet ratified the treaty, so the review probably signals a continuation of U.S. policy of waiting to ratify until other nuclear powers do so first.
Regarding the Intermediate-Range Nuclear Forces Treaty, the review states that “the United States will not forever endure Russia’s continuing non-compliance.” It warns generally against concluding further pacts with states that violate existing agreements and calls specifically for a response to Russia’s alleged treaty violations through “INF Treaty-compliant research and development.” This initiative would entail “reviewing military concepts and options for conventional, ground-launched, intermediate-range missile systems.” The review apparently seeks to encourage Russia’s return to compliance with the INF Treaty by developing—though not deploying—U.S. missiles.
Finally, the review rejects the Treaty on the Prohibition of Nuclear Weapons, arguing that the treaty is “fueled by wholly unrealistic expectations” of achieving nuclear disarmament without first transforming the international security environment.