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What will Biden do if Putin goes nuclear? Experts say a nuclear response is unlikely but not impossible

Russian military doctrine allows battlefield use of nuclear weapons, and the Biden administration has discussed possible responses.
Image: Russia nuclear missiles
Russian nuclear missiles drive along Red Square during the military parade marking the 75th anniversary of the Nazi defeat, on June 24, 2020, in Moscow. Mikhail Svetlov / Getty Images

It’s a troubling question with no palatable answer: What would President Joe Biden do if Russia used nuclear weapons in the Ukraine war?

A half dozen current and former government officials briefed on the issue, and several outside experts, told NBC News there was no playbook and little agreement about how the U.S. would respond to a norm-shattering act of destruction that could obliterate a Ukrainian city, kill tens of thousands and send a cloud of nuclear fallout drifting over NATO countries in Western Europe.

This isn’t new to the Biden administration. In fact, when the Obama administration conducted a war game simulating Russian use of nuclear weapons in the Baltics, there were fundamental disagreements about how to react. 

U.S. intelligence officials say they have seen no signs that Russian President Vladimir Putin is poised to employ so-called battlefield nukes, but several versions of Russian military doctrine published since 2000 have envisioned the first use of nuclear weapons in response to a conventional threat in a regional war in response to a conventional threat against the Russian homeland. And military experts say Russia’s smallest warheads have many times the explosive power of the bombs dropped on Hiroshima and Nagasaki.

As the U.S. continues to send ever more sophisticated weapons designed to help Ukraine destroy invading Russian forces, American officials tell NBC News the Biden administration has for months been thinking the unthinkable about what Putin could do — and war-gaming scenarios envisioning Russia using an atomic bomb on Ukraine.

“We don’t see … practical evidence at this point of Russian planning for the deployment or even potential use of tactical nuclear weapons,” CIA Director William Burns said last month. But, he added, “given the kind of saber-rattling that ... we’ve heard from the Russian leadership, we can’t take lightly those possibilities.”

NBC News talked to a half dozen current and former officials briefed on the issue, and several outside experts. Current officials declined to speak on the record, citing the sensitivity of the planning.

It’s fair to say that the American response “would depend wildly on how the Russians used” a nuclear weapon, as one U.S. official regularly briefed on U.S. government deliberations put it.

A demonstration shot over the Black Sea? A strike on Ukrainian troops in a remote area? Or far more provocative scenarios, such as a devastating blow to a major Ukrainian city or a nuclear attack on a NATO country?

The menu of American options is stark, officials and outside experts say: Stay the course, up the sanctions and keep arming the Ukrainians, while building an international coalition against Russia that completely isolates the country; launch a conventional military attack on Russian forces in Ukraine or Russia; or respond with a nuclear attack. Unless a NATO country was hit, the U.S. would not have any obligation to respond.

Some military and intelligence officials told NBC News they believe it’s unlikely the U.S. would retaliate militarily after a single Russian use of a so-called tactical nuclear weapon in Ukraine. Others said Biden would have to unleash some conventional force, perhaps attacking Russian troops in Ukraine or the Russian military unit that launched the nuclear weapon, an option that could have serious repercussions, since Russian military leaders might be killed.

If Russia used a nuclear weapon of any type, “I expect (the president) to say we’re in a new situation, and the U.S. will directly enter the war against Russia to stop this government that has not only broken so many international laws and violated human rights but also now violated the nuclear taboo,” said Evelyn Farkas, a former top Pentagon official for Russia and now executive director of the McCain Institute. “Putin will be signing the order on changing the regime.”

But two U.S. officials briefed on the issue did not agree, with one saying, “Unless they use them on NATO we’re probably not going to respond militarily.”

Under this thinking, Biden would not want to risk an escalation into a full-scale nuclear war that leads to the destruction of American cities. But he might not have to, because if Putin were to go nuclear, experts believe most other countries in the world, including many that are sitting on the fence in the current conflict, would quickly turn against and isolate Russia.

“The whole world would stop,” said Joseph Cirincione, a nuclear expert and distinguished fellow at the Quincy Institute for Responsible Statecraft.

A remote possibility that can’t be taken lightly

American and Western national security officials tell NBC News there has been no sign that Russia has moved tactical nuclear weapons out of storage facilities. Intelligence officials have said they assess that Putin would consider nukes only if he believed his regime was in mortal danger.

But two U.S. officials, citing American intelligence assessments, say some in Putin’s inner circle have encouraged him to test a nuclear weapon as a show of strength during moments when his conventional forces have struggled in Ukraine. The officials said there is continuing concern that Putin could choose this option if he believes Russia has been backed into a corner. 

Putin placed Moscow’s nuclear forces on high alert shortly after his invasion of Ukraine began on Feb. 24, and he warned that “no one should have any doubts that a direct attack on our country will lead to the destruction and horrible consequences for any potential aggressor.” But U.S. officials told NBC News they did not see any changes to their footprint or movements at the time. In April, Russian foreign minister Sergey Lavrov warned the West not to underestimate the elevated risks of nuclear conflict over Ukraine. Putin supporters on Russian state TV in recent weeks have talked openly about a nuclear war with the U.S. and Europe.

All this comes against the backdrop of a Russian nuclear doctrine that has evolved in what Western officials consider disturbing ways. In a 1993 document, Russia said it would use nuclear weapons only when the existence of the country was threatened. But in versions published since 2000, Russia reserves the right to use nuclear weapons in response to any weapons of mass destruction used to attack Russia and its allies, according to scholars who have examined it.

The doctrine also allows for the use of nuclear weapons “in response to large-scale aggression using conventional weapons in situations critical to the national security of the Russian Federation.” Experts have described that strategy as “escalate to de-escalate,” and they say it means that Russia is willing to make limited use of nuclear weapons to win what would otherwise be a conventional war.

On paper, U.S. nuclear doctrine is similar, but in practical terms, experts do not believe an American president would ever use nuclear weapons in a regional conventional war, and the U.S. has not, through Korea, Vietnam, Afghanistan and Iraq. Officials say the main purpose of the U.S. nuclear arsenal is to deter or respond to a nuclear attack by an adversary. Still, the U.S. has not ruled out using nuclear weapons in response to biological or chemical attacks, and in some limited circumstances, conventional attacks. It still maintains around 100 nuclear weapons in NATO countries, put there originally to stop Russian tanks from seizing Western Europe.

Nuclear warning shot?

Officials are struggling to understand exactly what could prompt Putin to use a nuclear weapon. To cement gains made on the battlefield? To reverse losses? To stave off a rout?

“It’s not clear where that red line is. If Ukrainian forces were to enter Russian territory, would that be sufficient? I don’t know," said Chris Chivvis, who served from April 2018 to April 2021 as the U.S. national intelligence officer for Europe.

Citing the Russian invasion of Georgia in 2008, its seizure of Ukraine’s Crimean Peninsula in 2014 and the Kremlin’s interference in the 2016 U.S. election, he added, “The reality is we have been surprised by Russia three or four times in the last 15 years.” 

Although technology exists to make battlefield nuclear weapons smaller than those dropped on Hiroshima and Nagasaki, Russia does not have warheads that small, according to Jeffrey Lewis, a nuclear expert at the Middlebury Institute. All of its so-called tactical nuclear weapons have enormous explosive power. There is no technological distinction between “tactical” nuclear weapons and “strategic” ones — the difference is in the targets and the goals. Tactical nukes are used to gain advantage on the battlefield, while strategic weapons are aimed at military infrastructure and even whole cities.

If Russia decided to use one, its options could include an attack on an airbase or other military target, an attack on a Ukrainian city or a test of a nuclear weapon at a remote site — a warning shot designed to signal Moscow’s willingness to use the ultimate weapon, former officials said. It could deliver the weapon as a bomb, or via a missile.

Although none of these scenarios are likely, the nuclear test could be the most attractive for Moscow, some experts said.

Testing a nuclear weapon would be an extraordinarily provocative step, something only North Korea has done in this century. 

A test above ground would risk radioactive material drifting into populated areas in Russian territory or NATO countries, depending on where it was carried out and the weather conditions. The former Soviet Union’s last nuclear test was carried out underground in 1989.

If Russia faced impending defeat in Ukraine, a single "demonstration attack," either on Ukrainian territory or possibly on the Black Sea, could seek to “convey their resolve, to try to force terror on the other party and get the Ukrainians to fold,” said Rose Gottemoeller, a former deputy secretary general of NATO who is now at Stanford University’s Freeman Spogli Institute for International Studies.

“They would be trying to strike terror into the hearts of the Ukrainians, get them to back down, get them even to concede defeat,” Gottemoeller said.

“Whatever he (Putin) did, he would do it in the belief that it would ensure his survival and perhaps compel surrender or retreat for the Ukrainians.”

Instead of a nuclear exchange with the U.S., “Russia has many options that it could employ either in Ukraine or elsewhere that would be much smaller steps up the nuclear escalatory ladder, but that nevertheless would represent a sea change in world history,“ said Chivvis, now a senior fellow at the Carnegie Endowment think tank. 

“I worry that people are not being open-minded to the reality that there are scenarios in which Russia could use nuclear weapons. They’re not the most likely scenarios, but to be responsible, we have to figure that into our thinking about this conflict,” he said.

Strategic ambiguity

The Biden administration has intentionally avoided spelling out how it would respond if Russia launched a nuclear attack in Ukraine, leaving open the possibility of retaliating with nuclear weapons, conventional forces, a cyber operation or other means.

“We have to be crystal clear in our policy of warning him of a swift and decisive response, without necessarily being unambiguous about what that would be,” said Alexander Vershbow, who served as deputy secretary general of NATO from 2012 to 2016 and as ambassador to Russia from 2001 to 2005.

Biden would have to at least consider a major conventional military response in support of Ukraine, former U.S. officials said.

A Russian attack on Ukraine with a tactical nuclear weapon would pose an excruciating dilemma for Washington and its NATO allies. Biden and Western political leaders would have to weigh a response that would avoid triggering a full-blown nuclear conflict with Russia, while still imposing a heavy cost on Moscow.

Jeffrey Edmonds, an expert on the Russian military at the CNA think tank, says there are four possible response scenarios, only two of which are plausible: Capitulate and sue for peace; stay the course with sanctions and pressure; mount a conventional attack to punish Russia; respond with a nuclear attack on Russia.

The real choice, he believes, is either staying the course or a conventional attack.

Biden could decide that “what we’re doing is working, we’re just going to keep going, we’re going to take the moral high ground.” 

Presumably, Russia would become more isolated diplomatically and international sanctions pressure would ratchet up. But Edmonds noted that calls for a military response to a Russian use of nuclear weapons would be “deafening” in Washington.

In his book “The Bomb,” about nuclear war planning, author Fred Kaplan writes about a National Security Council war game during the Obama administration that simulated a Russian tactical nuclear attack on a NATO country during a Russian invasion of one of the Baltic States. Lower level officials decided not to respond with a nuclear weapon, instead continuing to fight with conventional forces. But when the same scenario was presented to Cabinet level officials, they decided that the U.S. had to respond with a nuclear attack, and they targeted Russian ally Belarus. 

“I think that’s nuts,” Cirincione said. “There is a belief that you can have a limited nuclear exchange. You don’t want to get in that box, because once you are in that nuclear war-fighting mindset, you can’t control it.”

The Biden administration’s track record so far suggests it would move cautiously, in consultation with its European allies, and seek to avoid plunging the world into a nuclear conflagration, former officials said. 

The administration has faced criticism that it has moved too slowly to send advanced weapons to Ukraine, but the White House’s supporters say the administration has focused on avoiding actions that could escalate the crisis into a direct clash between Russia and the U.S.

Realistically, the U.S. would look for ways to respond short of launching a nuclear weapon, possibly through cyber operations or other support for Ukraine, said Gottemoeller. 

The United States would need to avoid any kind of nuclear escalation in the interest of the U.S. and its allies, but also for “global survival,” she said.