Size matters when it comes to nuclear weapons. Normally, big, powerful nations like big, powerful things, and few things are bigger or more powerful than nuclear weapons. But today the United States wants to go small. Is this a good thing?
The Trump administration’s 2018 Nuclear Posture Review calls for increasing the number of “low-yield” (what used to be called “tactical”) nuclear weapons in the US arsenal. Such weapons have an explosive output that is roughly 200 times smaller than that of the largest US nuclear weapons, but still on par with the bombs that destroyed Hiroshima and Nagasaki. Proponents claim that they offer increased flexibility and are necessary to address challenges from Russia.
Having more flexibility sounds like a good idea, but things are seldom as they appear when it comes to nuclear weapons. There are a number of arguments that critics have already raised that highlight possible drawbacks of the new low-yield weapon in the US nuclear arsenal. But there is another significant problem that has received scant attention in discussions among pundits and policy makers. Giving America’s leaders a greater range of nuclear options through low-yield weapons actually signals a lack of resolve, weakening the nation’s ability to stand toe-to-toe with adversaries, especially in light of US advantages in other domains. Simply copying Russia’s nuclear force structure in this way ignores the contrasting interests and vulnerabilities each nation faces in attempting to wield influence in world affairs.
What are they good for? What do low-yield nuclear weapons buy the United States that the nation’s strategic nuclear deterrent, or its superiority in conventional military domains, cannot? Low-yield nuclear weapons might allow a leader to exert influence in situations where the nation is unable to deploy significant conventional forces or is unwilling to commit the country’s strategic deterrent.
During the Cold War, America relied on the threat of nuclear retaliation to deter Warsaw Pact forces from invading NATO territory. This doctrine, part of President Eisenhower’s New Look strategy, was meant to compensate for an unfavorable balance of conventional forces between NATO and the Warsaw Pact. To substitute deterrence for defense in this way, US officials had to convince both NATO and the Warsaw Pact that America was willing to put Washington or New York at risk to defend Bonn or Paris. To this day, the United States openly declares its willingness to use nuclear weapons first, if necessary, although the circumstances under which it would do so are of course much more limited.
In recent years, however, with the collapse of the Soviet Union and subsequent decline in Russian military power, the shoe is on the other foot. NATO has major conventional advantages over Russian forces; today it is Russian President Vladimir Putin who must compensate for conventional weakness with nuclear bluster. The United States doesn’t need small nuclear weapons to act as a substitute for other forms of military power when America dominates in other military domains.
Exposing a lack of resolve. What the United States lacks are obvious reasons to fight wars in places that are distant from its shores or otherwise not vital to US interests. It is hard to see how tactical nuclear weapons would make US resolve appear more credible in an area such as Russia’s near abroad. On the contrary, deploying more low-yield weapons only highlights this unusual, and distinctive, area of contemporary US weakness.
The logic of nuclear security differs from that of conventional conflict. No sane person wants a nuclear war. Instead, as Thomas Schelling explained in the 1960s, nuclear weapons force nations to compete in terms of their willingness to risk nuclear war as an unintended consequence of competition. Much like teenagers playing a deadly game of chicken in their hot rods, the goal in nuclear brinkmanship crises is to get the other side to back down out of fear, rather than to actually demonstrate nuclear superiority on the battlefield. Shifting the competition from a process in which the winner is the state that is most likely to prevail militarily (a test of strength) to one in which the winner is the state that cares more (a test of wills) will generally disadvantage the more capable but less resolved state. In today’s world, it is the United States and its allies that are most often more capable but less willing to risk nuclear war.
The United States expanded its influence in the world enormously after the Cold War; it already dominates—and is unchallenged—in areas where its resolve is unquestioned. What remains in contention, and subject to increasing instability, are regions where US resolve is in some doubt, often for good reason. It would be bizarre for Americans to care equally emphatically about every place on the globe. So, US adversaries already know (or believe) that they are more resolved than the United States in some of these places, often because it is true. What they continue to fear are superior US capabilities. These adversaries would be outmatched militarily if the United States decided to thoroughly commit to a major conventional contest in a place like Ukraine.
In such circumstances, if Russia, a less capable but more resolved adversary, made a threat to use tactical nuclear weapons, the United States might well back down. Indeed, Vladimir Putin is said to have made precisely such a threat when faced with the possibility of NATO intervention in Crimea. In general, a weaker, more resolved country may be able to use nuclear threats to force a stronger, less resolved country to fold. So playing the nuclear card is especially attractive for a leader who expects to lose a conventional contest. But this is not America’s problem.
The United States could win most conventional contests, provided it is willing to make the investments required. So the only clear benefit of threatening to retaliate in-kind to a tactical nuclear attack would be to save cash or to avoid the human cost of battle. As a result, substituting “a comparatively low-cost” tactical nuclear weapon for conventional force paradoxically telegraphs a lack of resolve to allies and adversaries alike, in precisely the domain of competition where resolve is an essential ingredient to win.
Put simply, having the option to exercise limited nuclear war invites America to play its weakest hand, converting a contest it can win (conventional capabilities) into one it is likely to lose (nuclear resolve).
A similar dilemma exists in the case of a strategic nuclear option. Why doesn’t the United States simply threaten to retaliate with big nuclear weapons if Russia—or any other nation—ever tried to get away with a limited nuclear strike? Again, the most logical explanation is one of credibility: the Russians may not believe that that the United States is willing to risk full scale nuclear war in order to prevail in a given dispute. In this case, fielding tactical nuclear weapons in a crisis might convince friends and enemies alike that United States cares more than they imagined. In fact, this is exactly the thinking behind deploying low-yield nuclear weapons on US submarines.
However, an overlooked consequence of this strategy is that such an action may only confirm to an adversary that the United States lacks resolve and is indeed reluctant to commit its strategic nuclear forces. The low-yield option only equips US officials to demonstrate that they are unwilling to threaten the very worst, by giving them the ability to threaten something less. Half measures usually embolden adversaries rather than inhibit them.
Fewer options are better. If the question during the Cold War was whether America was willing to risk annihilation to protect Western Europe, today the equivalent comparison is whether America will sacrifice Washington or New York for Vilnius or Bucharest. If US leaders are not willing to take such a gamble, then it is far from clear that the United States gains anything from the false posturing made possible by possessing additional low-yield nuclear weapons. Indeed, the temptation will be for observers to further discount US willingness, increasing uncertainty and heightening the risk of a possible nuclear exchange.
The issue of low-yield nuclear weapons championed in the Nuclear Posture Review is a rare instance where more options are not better. Alternatives are always considered attractive to politicians, but as strategic theoreticians have long understood, reducing one’s options is the smart play in chicken, as it is in nuclear brinkmanship. America can already demonstrate its resolve by deploying its conventional forces or by committing its strategic deterrent. If it is unwilling to commit to either of these alternatives, then tactical nuclear weapons simply telegraph the fact that US interests are attenuated. On rare occasions when low-yield nuclear weapons would allow America to protect an ally, it can do so with existing capabilities, using options that are inherently more credible and more stable for world affairs.
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