Ask a Scientist: Confronting Putin’s Nuclear Threat

January 12, 2023 | 9:30 am
Wikimedia Commons/ The Council of the Federation of the Federal Assembly of the Russian Federation
Elliott Negin
Senior Writer

Russian President Vladimir Putin is playing a dangerous game of nuclear chicken.

Last February, on the very day Russia invaded Ukraine, Putin put the world on notice. “No matter who tries to stand in our way or all the more so create threats for our country and our people,” he said, “they must know that Russia will respond immediately, and the consequences will be such as you have never seen in your entire history.”

That warning was widely understood as a threat to go nuclear, especially when just three days later, he ordered Russian nuclear forces to be put on high alert, citing Western financial sanctions and “aggressive statements” by NATO members.

Months later, however, Putin brushed off such talk, denying he had any intentions of using nuclear weapons in Ukraine. “We have no need for that,” he said in late October. “There is no point in that, neither political, nor military.” He said his previous comments were in response to Western leaders’ own comments about using nuclear weapons.

That same week, however, Russia conducted an annual military exercise testing nuclear-capable missiles. US officials discounted the idea that the exercise was “some kind of cover activity” for using nuclear weapons in Ukraine, but shortly thereafter it was reported that senior Russian military officials had been debating when and how Moscow could use a battlefield nuclear device in Ukraine.

Adding yet another twist, in phone conversations with a handful of his NATO member counterparts in late October, Russian Defense Minister Sergei Shoigu alleged that Ukraine was planning to explode a “dirty bomb”—a conventional explosive device that disperses radioactive material—on its own territory and blame it on Moscow.

In a joint statement, the foreign ministers of France, the United Kingdom and the United States said their governments “reject Russia’s transparently false allegations.” Meanwhile, Ukrainian President Volodymyr Zelensky suggested that Shoigu was laying the groundwork for Russia to deploy a dirty bomb on Ukrainian soil and blame Ukraine—a classic “false flag” gambit. “If Russia calls and says that Ukraine is allegedly preparing something,” he said, “it means only one thing: that Russia has already prepared all of it.”

Then, in early December, Putin reassured the West that “under no circumstances” would Russia use nuclear weapons first. “We have not gone crazy,” he said. “We are aware of what nuclear weapons are. We have these means. They are in a more advanced and modern form than those of any other nuclear country, this is obvious. But we are not going to brandish these weapons like a razor, running around the world.”

Crazy or not, there is no way to know if Putin has really decided to sheathe his nuclear saber for good. After all, Russia’s recent threats against Ukraine are nothing new. It threatened Ukraine with nuclear weapons in 2014 when Ukrainian officials pledged to repatriate Crimea after Russia annexed it. A year later, Russia threatened to train its nuclear missiles on Danish warships if Denmark—one of NATO’s founding members—joined NATO’s missile defense system. What would happen if a cornered Putin changed his mind yet again and decided to do the unthinkable? How should the United States and NATO react?

To get a better understanding of the likelihood of Putin reversing his latest position and the fallout—in  every sense of the word—if he did, I turned to Eryn MacDonald, an analyst with the Union of Concerned Scientists (UCS) Global Security Program. Besides discussing the risks and consequences of the war in Ukraine during a UCS webinar last month, MacDonald also posted a column in November that described in detail the differences among tactical nuclear weapons, strategic nuclear weapons, and dirty bombs, which I used as a jumping-off point for our conversation.

EN: Before we talk about the potential consequences of Putin’s nuclear saber-rattling, it would be helpful if you explained what exactly a tactical nuclear weapon is, and how it is different than a strategic nuclear weapon and a so-called dirty bomb.

EM: The first key point is that a dirty bomb is not a nuclear weapon. Sometimes called a radiological dispersal device or a radiological weapon, a dirty bomb uses conventional explosives—such as dynamite—to disperse radioactive materials. There is no nuclear explosion. Dirty bombs would cause terror, not achieve a military objective. They have been called “weapons of mass disruption” as opposed to weapons of mass destruction.

The second key point is that both tactical—or “nonstrategic”—and strategic nuclear weapons are full-fledged modern nuclear weapons. Both rely on nuclear fission and nuclear fusion to release enough energy to create a fireball that reaches a temperature of tens of millions of degrees—the same as the center of the Sun.

So the modifiers “tactical” or “strategic” do not refer to any difference in the way the weapons operate. They may not even correlate with differences in the size of their explosive yields. Although they are often thought of as small, US and Russian tactical nuclear weapons have a wide range of yields, from less than a kiloton to more than 100 kilotons.

The only thing the two labels indicate are the weapons’ intended use. Shorter-range tactical weapons are for battlefield use while long-range strategic weapons are designed to fly hundreds or thousands of miles to attack an adversary’s homeland. That difference, however, may not amount to much in the real world. As then-US Secretary of Defense James Mattis explained in 2018: “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.”

EN: How much damage could a tactical nuke do? What about a dirty bomb? How do they compare to the bomb the United States dropped on Hiroshima in 1945? What would they really accomplish in the case of Ukraine?

EM: We should first note that a dirty bomb is in a totally separate category here. Most of a dirty bomb’s damage would be due to the explosion, so the number of deaths and amount of destruction would depend on the explosion size. Deaths from radiation would be rare and radiological contamination would be much less widespread than from a nuclear explosion—“within a few blocks or miles” compared to “thousands of square miles,” according to the US Nuclear Regulatory Commission. Even so, a dirty bomb would still require an extensive, expensive cleanup that could leave the contaminated area unusable for a long period of time.

The term “tactical nuclear weapon” covers a broad range of weapon types and yields. The nuclear bomb dropped on Hiroshima had a yield of roughly 15 kilotons. It instantly killed more than 70,000 people and reduced the city to ruins. Some US and Russian tactical nuclear weapons have yields several times larger, which gives you an idea of how devastating a tactical nuclear weapon could be.

Depending on the type of weapon, how it was used, the target’s population density, weather conditions, and other factors, exploding a tactical nuclear weapon could result in a wide range of outcomes. Even a single nuclear explosion could spread radiological contamination over a wide area if weather conditions permit. To realistically estimate the damage, you would have to model specific scenarios in detail.

More important, using any type of nuclear weapon could be the first step in an escalatory spiral that leads to a civilization-ending nuclear war.

Apart from its physical impact, any use of a nuclear weapon—even in a scenario with minimal destruction and few casualties—would be hugely damaging in other ways. First responders and medical personnel in even the most well-prepared cities would struggle to meet the overwhelming demand for help, and the situation would be far worse during a military conflict. There also would be psychological impacts and economic disruption worldwide. And it would break a taboo against the use of nuclear weapons that has not been violated since 1945, throwing into question the future of the entire international nonproliferation regime.

EN: How many tactical nuclear weapons do the United States and Russia have in their respective arsenals? Do the NATO countries that border Russia—Estonia, Latvia, Lithuania, Norway and Poland—have nuclear weapons on their soil? Do we know where Russia stores its nuclear weapons?

EM: The United States possesses about 200 B61 tactical nuclear gravity bombs that can be dropped from aircraft. These have adjustable explosive yields between 0.3 and 170 kilotons. It deploys about 100 of these bombs at bases in five European countries: Belgium, Germany, Italy, the Netherlands, and Turkey. None are deployed in the NATO countries bordering Russia.

Russia has a much larger number of tactical nuclear weapons—nearly 2,000. They range in yield from less than a kiloton to more than 100 kilotons and are normally kept in central storage bases, with warheads stored separately from their delivery systems. They can be delivered by air, ship, and ground-based systems, some of which also deliver conventional weapons. A number of the missiles Russia has launched against Ukraine also can carry nuclear warheads, which increases the potential for confusion.

EN: What are the likely scenarios if Putin uses a nuclear weapon? What could Russia possibly gain? What could it possibly lose?

EM: There has been a lot of speculation here. Some analysts have suggested Putin might use a nuclear weapon in a symbolic fashion, perhaps by exploding a single low-yield weapon in an uninhabited area, such as over the Black Sea, to warn NATO against providing more aid to Ukraine.

Putin deciding to use tactical nuclear weapons as part of a warfighting strategy seems highly unlikely. Analysts have pointed out that using nuclear weapons to achieve a particular military objective would almost certainly require using multiple tactical nuclear weapons with largely unpredictable physical and strategic consequences. The fallout could endanger Russian troops and civilians in Russian-controlled areas.

Both the United States and Russia eventually realized that nuclear weapons—even tactical weapons supposedly meant for battlefield use—are very difficult to use in a militarily effective way. Their use is far more likely to lead to uncontrolled escalation, an outcome neither side wants. US wargames involving tactical nuclear weapon use, for example, predict a rapidly spiraling out-of-control scenario, and a recent Princeton University simulation of a US-Russian conflict that escalates from tactical nuclear weapons use to all-out nuclear war estimated more than 90 million dead and injured.

Russia has more to lose than gain from using a nuclear weapon in Ukraine. The US and NATO reaction would be swift and decisive. It likely would further strengthen opposition to Russia’s invasion and result in additional Western aid to ensure that Russia’s egregious violation of international norms was not rewarded. Russia also would become even more of an international pariah, potentially losing the economic partners that have so far stood by it, most notably China and India.

EN: What do you think the United States and NATO should do if Putin uses a nuclear weapon?

EM: The Biden administration and top US political and military leaders, along with their NATO counterparts, have undoubtedly discussed this possibility at great length and put together plans for a wide range of contingencies. So, from my standpoint, the most important thing is to be clear about what the United States and NATO should not do. They should not respond in kind by using a nuclear weapon. That is the one reaction that would be most likely to take us down a dangerous road of escalation that could lead to all-out nuclear war.

EN: Stephen Young, senior Washington representative for the UCS Global Security Program, wrote in a column for Politico Magazine last September that Putin’s threat to use a nuclear weapon in Ukraine heralds what has been called the “age of predatory nuclear weapon states.” What did he mean by that—and what are its implications?

EM: Young was referring to the idea that nuclear weapon states can undertake major conventional military actions while relying on their nuclear capability to prevent outside interference, which is what Russia did in Ukraine. Instead of employing nuclear weapons as weapons of last resort to deter or defend against an attack on their homeland or their allies, predatory nuclear states can use them as a cover for aggressive military expansion. Because the threat of nuclear war is sufficiently terrifying, lower-level conflict becomes more feasible.

The implications are serious, but not surprising. Both the Soviet Union-Russia and the United States have historically used nuclear “signaling”—somewhat more subtle types of threats, such as deploying nuclear-armed bombers to a particular area or issuing statements alluding to potential nuclear use—to persuade adversaries to stay out of areas or situations they considered to be their exclusive domain. The current situation in Ukraine is a more blatant example of this dynamic.

EN: There has been some movement to address some of Young’s concerns. For example, as of last fall, more than 90 countries have signed the Treaty on the Prohibition of Nuclear Weapons and nearly 70 have ratified it. Have any nuclear-capable states signed it? What impact could the treaty have?

EM: Work around the ban treaty has helped bring to the forefront the humanitarian consequences of nuclear weapons, bringing in voices previously shut out of the conversation and rallying activists who refuse to continue to condone the dangerous, immoral, and undemocratic nuclear weapons system under which we have all lived for so long.

The treaty’s long-term impact remains to be seen, but the fact that it reached the required number of ratifications to enter into force is remarkable, given that no nuclear weapon state has signed it, and the United States has been downright hostile to it.

The humanitarian consequences movement’s efforts that led to the treaty are changing the conversation about nuclear weapons, stigmatizing these weapons for the suffering they would cause rather than confining the discussion to the sterile realm of military strategy. For example, the G20 nations—which include all of the internationally recognized nuclear weapon states—issued a surprisingly strong statement last November declaring that “the use or threat of use of nuclear weapons is inadmissible,” language that is similar to the ban treaty itself. Russia, I should note, was not in attendance.

EN: Finally, what can the general public do to promote a nuclear-free world? It’s very easy to feel helpless. Are there concrete things people can do?

EM: Unfortunately, nuclear weapons decision making is restricted to a small circle of insiders—the “nuclear priesthood”—and ordinary citizens are typically told they don’t know enough to be involved. But even if nuclear weapons are never used again, their very existence affects us all. Residents of nuclear weapon states and non-nuclear weapon states alike live with the daily possibility that these weapons could end their lives, or even our entire civilization. And, in any case, the production, testing, maintenance, and disposal of these weapons has already caused a great deal of harm, particularly for marginalized communities.

The nuclear ban treaty shows that non-nuclear weapon states were able to attain standing in the international debate over these weapons that nuclear weapon states long denied them. Individuals can do the same by getting involved in organizations such as Back from the Brink, a grassroots effort cofounded by UCS that promotes policies that organizations and elected officials at the state and local level can endorse. So far, the effort has the support of more than 300 elected officials, some 60 municipalities and counties, and seven state legislative chambers. UCS also offers opportunities to get involved by joining the UCS Science Network or petitioning Congress to support less risky nuclear weapons policies. There is much work to do, and the need has never been more urgent.