What Are 'Low-yield' Nuclear Weapons?

usable, nukes — In the 2018 Nuclear Posture Review, the Trump administration says it wants to increase the existing U.S. low-yield capability, which now consists of about 500 gravity bombs that could be dropped by U.S. aircraft, including about 200 positioned in western Europe. David Hills/Getty Images

During the 2016 presidential campaign, MSNBC host Joe Scarborough caused a stir by saying that then-candidate Donald Trump repeatedly had asked a foreign policy adviser why the U.S. couldn't use the nuclear weapons in its arsenal. A Trump spokesman later denied that Trump had posed this question.

Nevertheless, since Trump became president in 2017, his administration has moved not only to expand the U.S. nuclear arsenal, but to add more "low-yield options" — smaller-scale nuclear weapons that a president could resort to using in something short of an all-out nuclear war.

In the 2018 Nuclear Posture Review, a document issued earlier this year, the Trump administration says it would increase the existing U.S. low-yield capability — which now consists of about 500 gravity bombs that could be dropped by U.S. aircraft, including about 200 positioned in western Europe — by modifying existing submarine-launched ballistic missiles to carry low-yield warheads. It also would develop a new class of cruise missiles to deliver low-yield nukes.

The Trump administration insists that it's not actually looking to use low-yield nukes. "To be clear, this is not intended to, nor does it enable, 'nuclear war-fighting,'" the National Posture Review notes. "Expanding flexible U.S. nuclear options now to include low-yield options is important for the preservation of credible deterrence against regional aggression. It will raise the nuclear threshold and help ensure that potential adversaries perceive no possible advantage in limited nuclear escalation, making nuclear employment less likely."

Though Trump, at his recent summit with Russian President Vladimir Putin in Helsinki, expressed a desire for a friendlier relationship with Russia, the National Posture Review portrays Russia, which is modernizing its stock of 2,000 low-yield nuclear weapons, as its expected adversary in such a limited nuclear confrontation. "Russia's belief that limited nuclear first use, potentially including low-yield weapons, can provide such an advantage is based, in part, on Moscow's perception that its greater number and variety of non-strategic nuclear systems provide a coercive advantage in crises and at lower levels of conflict," the report says. "Recent Russian statements on this evolving nuclear weapons doctrine appear to lower the threshold for Moscow's first-use of nuclear weapons."

Not a Useful Deterrent

But nuclear arms-limitation advocates don't seem to be comforted by the Trump administration's assurances that it only wants low-yield nukes as a deterrent.

"Because the U.S. president might actually use these weapons, they argue that it better deters the use by another country," says Daryl G. Kimball, executive director of the Arms Control Association, a Washington, D.C.-based nongovernmental research and policy organization that works to reduce the threat of nuclear war. "But the problem is that there's no such thing as a mini-nuke."

Kimball notes that the destructive potential of the low-yield, nonstrategic weapons is still enormous — only slightly less than the bomb that destroyed Hiroshima in 1945 and, by one estimate, killed between 90,000 and 166,000 people. Depending upon where a low-yield weapon lands, "it still has city-killing potential," Kimball says.

Beyond that, he notes, in the event that the U.S. and another country actually started tossing low-yield nukes at one another, there's no guarantee that the conflict wouldn't escalate into an all-out nuclear war. (Remember that it only took a few pistol shots fired by a lone assassin to trigger World War I.)

As Kimball points out, the U.S. already has low-yield nuclear weapons positioned in western Europe to deter Russian aggression. "In our view, it's overkill and unnecessary to add more low-yield weapons." The Russians' low-yield nukes only provide a "a cynical reason to plunge ahead," he says.

"What we really need is for the U.S. and Russia to refrain from developing and deploying new types of nuclear weapons," Kimball says. "Each side already has a diverse and deadly arsenal. The two sides need to sit down together and discuss how we can maintain existing treaties and reduce the arsenals."

New START

In particular, according to Kimball, it's crucial for the U.S. and Russia to renew the New Strategic Arms Reduction Treaty, an eight-year-old agreement that caps the deployed nuclear warheads for each side at 1,550, among other provisions. New START expires in 2021, and unless the two countries return to the bargaining table and come to a new agreement before then, "there will be no legally binding limits on the two nations' arsenals," Kimball warns.

In an interview with Fox News after the Helsinki summit, Putin said he had assured Trump that the Russians wanted to extend New START, but added the caveat that "we have to agree on the specifics at first because we have some questions to our American partners."

One potential sticking point in the negotiations is that the U.S. has for several years accused Russia of violating another nuclear arms limitation treaty, the 1987 Intermediate-Range Nuclear Forces Treaty, by deploying nuclear-tipped cruise missiles. Russia has denied the allegation.

It's also unclear whether Trump will want to renew New START. He reportedly was unfamiliar with New START and denounced it as a bad deal negotiated by the Obama administration in a January 2017 phone conversation with Putin, according to Reuters, which cited two current and one former U.S. official with knowledge of the call. Since then, Trump hasn't shown any sign of interest in renewing the treaty, according to a February 2018 Foreign Policy article by John Wolfsthal, director of the Nuclear Crisis Group and a former National Security Council official in the Obama administration.