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If Putin Were to Use Nuclear Weapons, What Would Follow?

Weighing terrible risks.
March 23, 2022
If Putin Were to Use Nuclear Weapons, What Would Follow?
Abstract illustration: radiant light beams rising from the horizon

Yesterday, Kremlin and White House officials answered questions about what might happen if Vladimir Putin’s invasion of Ukraine goes nuclear.

When asked by CNN’s Christiane Amanpour about the conditions under which Putin would order the use of nuclear weapons, Putin spokesman Dmitry Peskov replied, “if it is an existential threat for our country, then it can be.” This quickly led to speculation about whether Putin might consider a threat to the continuation of his regime as sufficiently “existential” to warrant the use of nuclear weapons.

In White House press briefing room yesterday, a reporter asked National Security Advisor Jake Sullivan whether President Joe Biden would discuss with other NATO leaders the possible use by Russia of nuclear weapons. “Well, President Putin, in the early days of the conflict, actually raised the specter of the potential use of nuclear weapons,” Sullivan replied. “We are constantly monitoring for that potential contingency. And of course, we take it as seriously as one could possibly take it.” Biden likely would be discussing “potential responses” with NATO leaders, Sullivan said.

So far, President Biden has chosen to proceed calmly. On March 11, he warned that “Russia would pay a severe price” if chemical weapons were used in Ukraine but remained silent about nuclear weapons (although senior administration spokesmen acknowledged that possible Russian nuclear use was being closely watched). Any military preparations, if there are any, were not announced. The strategy was to ignore the nuclear threat as if it had not been made. This may have been the wisest course, but it may have had the effect of further convincing Putin that he has to do something that cannot be ignored. This week, Biden intensified his rhetoric, saying that Putin’s “back is against the wall” and that Russian propaganda about Ukraine supposedly having biological and chemical weapons is “a clear sign he is considering using both of those.” He reiterated the unspecific threat of “severe consequences.”

Earlier this month I wrote in The Bulwark that as the war goes worse for Putin his incentives for using nuclear weapons go up. Well, the war is going worse for him. If Putin were to use chemical weapons, he would test NATO resolve. NATO may be able to deter Russian nuclear weapons use by mounting a fierce and violent response to Russian chemical weapons use. It should prepare to do so.

What if NATO responds with more sanctions but not military intervention, and Putin raises the stakes again? Some commentators appear to assume that NATO at that point would have to back down, however tragic that might be, to avoid a nuclear war. It may be the case that any NATO action that could increase the risk of nuclear war is unacceptable. That is what Putin is counting on. A small risk of a nuclear war that kills millions may well be unacceptable to us and our allies. We may decide it is, but we should do so with an understanding of what will follow. Putin and Putinism will be understood to be victorious. If one nuclear-armed nation can commit clear acts of international aggression against a non-nuclear nation and then shut down military responses by using nuclear weapons in a limited manner, other nations with aggression in mind will surely take note. Chinese nuclear coercion would become part of any plan against Taiwan. North Korean nuclear coercion would be revived. If Iran were to acquire nuclear weapons, Iranian nuclear coercion of Saudi Arabia, though not of Israel, would become a real possibility. NATO would need to deploy nuclear weapons to the Baltic states to defend them. Former Japanese Prime Minister Shinzo Abe called for the deployment of U.S. nuclear weapons to Japan after the invasion of Ukraine. After a Russian victory, the Japanese government might ask for such deployments. In which case, China would be furious. Other countries on the fence about getting their own nuclear weapons will decide that they must. The point is that taking action against Putin even though he uses nuclear weapons has risks, but not taking action also has risks. They are just a little bit further down the road.

This does not justify any and all calls to arms. Sending long-range Russian surface-to-air missiles such as the S-300s in NATO arsenals would make it more complicated for Putin to launch a missile with a nuclear warhead, and such transfers are receiving more support, since there are reports of Ukrainian defenses intercepting missiles. But Putin can salvo missile launches within which one missile has a nuclear warhead, and the defender may not know which to shoot at. What else can be done without undue risk?

The formidable array of U.S. systems that can detect the launch of missiles should be on high alert. U.S. systems, such as the AEGIS anti-missile system, should also be on high readiness.

But what if a nuclear warhead gets through and detonates on Ukrainian soil? We should still rely on nuclear deterrence to prevent Putin from using nuclear weapons on a larger scale. It may be possible if difficult to keep a war limited after one nuclear weapon is used. If Putin uses many, he knows that Russia will certainly face nuclear retaliation. But that logic suggests that the United States could turn the table on Putin. If he invades a non-NATO country and uses a nuclear weapon, the gloves should be off with regard to NATO non-nuclear military strikes against Russian military forces in Ukraine and Belarus. The political goal should be—must be—to deny a nuclear aggressor victory, because the global consequences would be dire.

In short, standing up to a Putin who used a nuclear weapon is risky. Living in a world in which there are many nuclear Putins may be even more risky. We should decide which risk is more acceptable, and prepare accordingly.

The immediate implications are clear. The United States should raise the Russian chemical and nuclear weapons contingencies with NATO and propose that NATO begin mobilization for non-nuclear action against Russian forces in Ukraine and Belarus in retaliation. This would primarily mean that NATO air forces, which are already flying patrols with armed weapons, should make plans for air-to-ground strikes against Russian forces. If NATO does not wish to do this, we should discuss what the NATO defense posture should be after Russia conquers Ukraine.

We are enjoying a moment when heroism looks like it will succeed at a high cost to Ukraine, but at a low cost to us. Putin may not let us continue to enjoy that moment much longer.

Stephen Peter Rosen

Stephen Peter Rosen is the Beton Michael Kaneb Professor of National Security and Military Affairs at Harvard University.