Would the United States ever actually use nuclear weapons?

The Syrian regime’s large-scale use of chemical weapons has prompted a vigorous discussion about whether the United States should respond with military force, and if so, how. Those advocating the use of force have debated options ranging from limited cruise missile strikes to a much larger campaign designed to mortally wound Syrian President Bashar al-Assad’s regime.

One military option that has thankfully not been part of the debate is the use of nuclear weapons. Yet unbeknownst to many, the most recent Nuclear Posture Review—a US government assessment of the proper role of nuclear weapons—technically does not rule out using them in response to nuclear, biological, or chemical weapons use by states, like Syria, deemed to be in noncompliance with their nonproliferation obligations.

There is, on the other hand, apparently universal agreement that using nuclear weapons in the midst of another country’s civil war would be wildly inappropriate and ineffective. But Syria’s use of chemical weapons raises several important questions that bear on US policy: If Washington wouldn’t consider using nuclear weapons even where its own official policy allows it, under what circumstances would it actually contemplate using them? And if it did, how many might it use?

Apart from responding to another country’s first use, the scenarios under which a US president would consider authorizing the use of these weapons are so limited as to be almost inconceivable. Moreover, if the president did use nuclear weapons, he or she would likely need only a handful, not the thousands the United States currently possesses. While nuclear weapons still retain value as a deterrent, changing geopolitical and technological conditions have made them a niche weapon, not the bedrock of US security that some still claim they are.

Who would America nuke? According to the 2010 Nuclear Posture Review, the United States will not use or threaten to use nuclear weapons against non-nuclear weapons states that are party to the Nuclear Non-Proliferation Treaty and are deemed to be in compliance with their nuclear nonproliferation responsibilities. It also states that the United States would only consider using nuclear weapons in extreme circumstances to defend the vital interests of the United States or its allies and partners. Based on these criteria, the United States would consider using nuclear weapons against states that possess nuclear weapons—Russia, China, France, the United Kingdom, India, Pakistan, Israel, and North Korea—as well as states that are in noncompliance with their nonproliferation objectives, namely, North Korea, Syria, and Iran.

France, the United Kingdom, India, and Israel can quickly be eliminated from the list of possible targets because they are not US adversaries. And even though the United States is often at loggerheads with Pakistan, it currently doesn’t fit the profile of a military adversary. Using nuclear weapons against Syria and Iran, meanwhile, is at this time surely off the table because neither possesses nuclear weapons and the United States could obliterate either country with conventional weapons.

That leaves Russia, China, and North Korea as the only theoretical targets of a US nuclear attack.

How much is enough? According to the latest estimates, the United States maintains an active stockpile of approximately 4,650 nuclear warheads, the vast majority of which are 10 to 50 times more powerful than the bombs that were dropped on Hiroshima and Nagasaki at the end of World War II. It is impossible to conjure up a believable scenario whereby the United States would use 500 of these weapons, let alone nearly 5,000.

Of the three states against which the United States would consider using nuclear weapons, only Russia possesses a nuclear arsenal that numbers in the thousands. Together the two countries hold nearly 95 percent of nuclear warheads on the planet, with no other country believed to possess more than 300. The only rationale for such large US and Russian arsenals is to target the other’s nuclear forces. Yet even though Washington and Moscow continue to deploy their forces as if the threat of global thermonuclear war were a distinct possibility, the reality is that such a conflagration is highly unlikely. The current downturn in relations over issues like Syria and National Security Agency leaker Edward Snowden may scuttle hopes for another formal arms control agreement, but the two countries are not enemies like they were during the Cold War.

While direct Russian aggression against the United States is highly improbable, some argue that America should retain the ability to threaten using nuclear weapons to deter a Russian conventional attack against a NATO ally, such as one of the Baltic states. The dubious effectiveness of such a threat aside, the best the United States could do with nuclear weapons if Moscow decided to invade, say, Lithuania, would be to repel the aggression and attempt to deter Russia from future conventional or nuclear attacks. But Washington would not be able to use nuclear weapons to eliminate Russia’s arsenal or change the regime in Moscow without inviting unacceptable damage in return. Thus, drastically fewer than the 1,550 strategic warheads the United States and Russia are each allowed to deploy under the New Strategic Arms Reduction Treaty would be sufficient to defeat the immediate aggression against an ally and attempt to deter further escalation.

And what of China, which is believed to have fewer than 300 nuclear warheads, and North Korea, which has fewer than ten warheads and—as of now—an uncertain ability to deliver them? It is difficult to imagine the United States using nuclear weapons against either country. In the case of China, security dilemmas involving Beijing and US allies over the status of Taiwan and the disputed islands in the South and East China Seas are potential flashpoints, but all the parties have a strong interest in avoiding military escalation. In the case of North Korea, Washington could destroy what few valuable targets the regime has using conventional weapons.

Nevertheless it is possible to imagine scenarios, however unlikely, in which the US government might consider using nuclear weapons against either country. It might retaliate against first use, retaliate against a major conventional attack that threatens the existence of a US ally, or launch a decapitating first strike in a deep crisis. But given the relatively small Chinese and North Korean nuclear arsenals and the potency of US conventional forces, the quantity of US nuclear weapons required would number not in the hundreds but the dozens. There are simply not enough plausible targets for anything more than that.

Critics of this line of reasoning are likely to argue that while a limited number of nuclear weapons may be sufficient to achieve war aims, many more are necessary to deter adversaries from attacking either the United States or its allies. Yet what threats now deterred by an arsenal of nearly 5,000 warheads couldn’t be deterred by many fewer weapons? And if a country couldn’t be deterred by a level half the size of the current US stockpile, what logic presumes it would be deterred by the current level?

Impractical and costly. The fact is, nuclear weapons are of diminishing strategic and military use to the United States, as the debate about whether to use military force in Syria demonstrates. As nuclear security and nonproliferation expert James Doyle points out, with the possible exception of North Korea, no other nuclear power “has state goals or conducts a foreign policy fundamentally hostile to the interests of the United States.” The nonnuclear threats that currently face the United States and its allies do not rise to the level of requiring a nuclear response. US conventional forces are unrivaled, which gives Washington the capacity to achieve almost every conceivable war aim without using nuclear weapons. Consequently, it is nearly impossible to imagine a situation where the first use of nuclear weapons wouldn’t greatly undermine US power and standing in the world.

Given the decreasing role that nuclear weapons play in US security policy, the arsenal is undoubtedly far too big. But in addition to working towards reducing the size of the arsenal, the United States should further circumscribe the scenarios under which it would consider using nuclear weapons. It can do this by transitioning from a posture that is still heavily based on first use to one more focused on retaliation. Ensuring that the tradition of nuclear non-use continues depends on it.