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Nicholas Miller is an Associate Professor in the Department of Government at Dartmouth College. He’s an expert on nuclear proliferation and international security. Our questions are in bold, his answers in quotation marks.

Can you explain the difference between tactical nuclear weapons and strategic nuclear weapons?

“Tactical nuclear weapons are generally lower-yield, shorter-range and are intended to be used on the battlefield. Strategic nuclear weapons are generally higher-yield, longer-range and intended to be used against adversary population centers or major military or command and control targets in the adversary’s homeland.”

Can you tell us a little about Russian nuclear doctrine and how it relates to the war?

“According to Russia’s stated nuclear doctrine, nuclear weapons would only be used in retaliation for an adversary nuclear attack or if the Russian state faces an existential threat from conventional attacks.
The concern with the current war is twofold: (1) Putin could decide to go nuclear regardless of what Russian doctrine says, and (2) there is ambiguity as to how to define an existential threat. While no one is worried about the US or NATO launching a nuclear first strike against Russia, it is possible that Putin could decide that a total conventional defeat at the hands of Ukraine (or NATO if they intervene) does pose an existential threat—if not to the Russian state, then to his grip on power, two things he may conflate.”

Under what scenarios could you see Russia use nuclear weapons against Ukraine? What might Putin target and why?

“I think Putin would only consider using nuclear weapons if the situation was very desperate—as noted above, perhaps if he thought he was on the brink of a decisive defeat in Ukraine that might threaten his grip on power. What exactly would such a decisive defeat look like? It’s very difficult to know how Putin might define this, but some possibilities could include losing much or all of the territory Russia took from Ukraine in 2014 or the initiation of significant Ukrainian operations on Russian territory itself.
What Putin would target is also highly uncertain, but I would guess he would use one or a few tactical nuclear weapons against Ukrainian military or infrastructure targets, with the aim of both slowing the Ukrainian advance and—more importantly—signaling the possibility of even greater escalation unless Ukraine and its Western supporters backed down.”

There are multiple examples of great powers that have lost wars and refrained from using nuclear weapons, like the United States in Vietnam and the Soviet Union in Afghanistan. Why should this be any different?

“It probably won’t be. I do think the odds are low in an absolute sense. But we shouldn’t forget that Nixon considered using nuclear weapons in Vietnam and Eisenhower had plans in place to use them if peace talks in Korea failed. We should also acknowledge that Ukraine is more geopolitically significant to Russia than Afghanistan was or than Vietnam or Korea were to the United States.”

What could the West do to dissuade Putin from using nuclear weapons against Ukraine?

“What I would advocate is making it clear that the use of nuclear weapons would only strengthen Western support for Ukraine, would risk making the economic sanctions permanent as long as Putin is in power, and could lead to direct NATO intervention.”

What kind of signals would you expect to see before a Russian nuclear strike?

“There are a number of things you might see, including public threats hinting at escalation if Ukraine doesn’t back down and Russia moving its strategic and tactical nuclear forces into a higher state of readiness and dispersal (both as a coercive signal, to prepare for use, and help complicate US preemption). As Barry Posen has argued, this process in and of itself could be very dangerous, leading the US to ready its nuclear forces in response, heightening the risk of catastrophic accidents or miscalculations.”

How could Russia’s invasion of Ukraine escalate into nuclear war between Russia and NATO?

“I can imagine a couple avenues. In theory, the US could respond to a nuclear strike against Ukraine with a tit for tat nuclear retaliation against Russia. The honest truth is no one knows what would happen next—it could escalate into major nuclear war or one side could blink and back down at an early rung in the “escalation ladder”. But I don’t think this would be the likely US response to nuclear use in Ukraine.
A more likely pathway would be that NATO decides to directly intervene against Russia in Ukraine, either because of some particularly egregious Russian atrocity, or the gradual expansion of war aims, and that this leads Putin to believe he faces imminent defeat and possibly being deposed at home. In this context, he might launch a limited nuclear strike against NATO targets to try to change the Western calculus.”

There’s been a lot of talk about the power of Russian nuclear weapons but what about NATO? What impact would all-out war have on Russia and Putin personally?

“A war between NATO and Russia that stayed conventional would almost certainly end in Russian defeat, given how poorly they’ve performed against Ukraine on its own. This could in turn threaten Putin’s grip on power. The problem is that—precisely for this reason—no one can be confident such a war would stay conventional.”

What is a question you wish you were asked and what is your answer to it?

“Why do you support huge Western aid and arms supplies to Ukraine given your concerns about Russian nuclear use?
Ukraine has a right to defend itself from aggression and the U.S. and NATO have an interest in showing that conquest doesn’t pay. It’s highly unlikely that Russia would go nuclear or even attack NATO conventionally in response to this sort of indirect involvement (this is a norm that was established during Cold War proxy conflicts). However, at some point, it is possible that Western support could start raising the risk of nuclear use, if, for instance, Ukraine seemed to be close to decisively defeating Russia. This would pose a difficult dilemma for Western policymakers.”

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The Hundred

Interview: The Danger of Nuclear Escalation