The Trump administration’s Nuclear Posture Review (NPR), released in February of this year, calls attention to the composition of the US nuclear arsenal and its adequacy as a deterrent. The NPR calls for a new lower-yield submarine-launched nuclear warhead, arguing that it is needed to “counter any mistaken perception of an exploitable ‘gap’ in U.S. regional deterrence capabilities.” We decided to put together the chart in Fig. 1 to illustrate the range of nuclear weapons already available in the US arsenal.
One thing that this visual immediately makes clear is that it would be difficult to perceive any real gap in US capabilities—the existing arsenal certainly does not lack for nuclear options for any occasion.
The blue bars in the image above each represent the explosive power, in kilotons, of an existing weapon or weapons in the US arsenal. As you can see, the US already has weapons with yields ranging from 0.3 to 1,200 kilotons—from 1/50 to 80 times the yield of the roughly 15 kiloton bomb that the United States dropped on Hiroshima in WWII (represented by the dotted bar in the chart). On the lower-yield side, the US currently deploys around 450 weapons, sometimes called “tactical nuclear weapons,” that have options for yields ranging from 0.3 to 10 kilotons. These include both an air-launched cruise missile and gravity bombs. It also deploys another roughly 2,000 weapons with higher—in some cases much higher—yields, ranging from 45 to 1,200 kilotons.
Still, the administration is proposing to fill this non-existent gap with a new lower-yield submarine-launched warhead, called the W76-2—the orange bar in Fig. 1. This new warhead would reportedly have a yield of 6.5 kilotons—right in the middle of the range of existing US low-yield nuclear options. “Low”-yield in the case of 6.5 kilotons, however, is a pretty questionable description. As noted above, the nuclear bomb that the US dropped on Hiroshima in WWII had a yield of roughly 15 kilotons—a little more than twice that of the proposed new weapon. It killed 100,000 people and reduced the city to rubble.
Labeling such deadly and destructive weapons “low-yield” may give leaders the dangerous impression that using them is not as serious as using a nuclear weapon with a larger yield, and that their use would not lead to full-scale nuclear war. But in reality, no one knows what would happen if a nuclear weapon—of any size—were once again used in war. As Defense Secretary James Mattis has said,
“I don’t think there’s any such thing as a tactical nuclear weapon. Any nuclear weapon used at any time is a strategic game changer.”
The administration’s choice of language in the NPR rationale for the new warhead is also interesting. It does not argue that such a gap actually exists, but that it is concerned that an adversary might mistakenly perceive one. While perceptions are always an important consideration in deterrence, it’s useful to keep in mind the fact that 1) we don’t actually know what our adversaries are thinking, and we’ve been dangerously wrong in past guesses; and 2) trying to ensure that no country could ever possibly perceive that it might have any type of military advantage is how arms races happen. Most relevant in the current situation, it is how the US and Soviet Union ended the Cold War with arsenals of tens of thousands of nuclear weapons each. This type of thinking is not about deterrence, but about “escalation dominance” and “nuclear warfighting,” both of which are even more unstable and dangerous.
Recognition of the particular dangers of low-yield nuclear weapons has, until recently, been widespread and bipartisan among US military and political leaders. Over the past several decades, the United States has eliminated much of its arsenal of low-yield nuclear weapons for this and other reasons. The Trump administration’s new move to develop more of these weapons is a step in the wrong direction that is both unnecessary and dangerous.
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