How the Ukraine war could go nuclear

Not since the Cold War has the specter of nuclear war hung so heavily over a president's crisis diplomacy.

As President Joe Biden meets with fellow NATO leaders, calls for a ceasefire in Ukraine are growing more urgent than ever — to alleviate the widespread human suffering but also to dial back what veterans of nuclear planning consider an alarming potential for it to spiral into a clash of atomic superpowers.

The nuclear brinkmanship from Russian President Vladimir Putin in recent weeks is unprecedented: He ordered a snap nuclear war game before the invasion and days later put his nuclear forces on high alert. And the Kremlin has repeatedly signaled it could resort to nuclear weapons — an option explicitly reserved in Russian military doctrine — if it determines the West’s intervention in the conflict goes too far.

Again on Tuesday, in an interview with CNN, Putin’s chief spokesperson refused to rule out the use of nuclear arms in the conflict.

So far, Biden has sought to dial down the tensions. The Pentagon has not changed the alert status of U.S. nuclear forces and military leaders have publicly said they have not detected Russian actions suggesting they are preparing to use nuclear weapons. The Pentagon also took the unusual step early in the conflict of putting off a regularly scheduled test of an intercontinental ballistic missile to avoid fueling nuclear tensions.

Yet as the conflict drags on, and Russia's conventional forces suffer surprisingly heavy losses while its economy reels, the prospect that Putin might resort to using weapons of mass destruction is increasing. Moscow has already demonstrated that it’s willing to use hypersonic missiles for the first time in a war.

With limited contact between the Kremlin and Western capitals, the risk that Moscow’s intentions could be misread with catastrophic consequences will only grow more acute, according to numerous specialists.

“There has always been a chance of mistakes, but I think the chances are much higher,” said former Sen. Sam Nunn, the longtime chair of the Armed Services Committee and now co-chair of the nonprofit Nuclear Threat Initiative. “I think we are in a different era in terms of blunders.”

It is a high-wire act confronting Biden as he tries to stiffen the spines of NATO countries for what is expected to be a long struggle. Allies are helping Ukraine fend off its bigger aggressor — including sending more arms and U.S. troops to defend NATO’s eastern borders — while not pushing Putin over the edge.

Russia invaded Ukraine as cooperation between Washington and Moscow on nuclear arms control has been unraveling in recent years. The two countries have walked away from several treaties to control the deadliest weapons, including one that outlawed intermediate-range nuclear missiles that could threaten Europe.

The only remaining nuclear pact between the two sides is the New Strategic Arms Reduction Treaty, which limits deployed strategic weapons to 1,550 each. Biden and Putin agreed last year to extend it until 2026.

But the treaty does not cover any of the thousands of smaller, or “battlefield,” nuclear weapons in their respective arsenals, including at least 2,000 in Russian stockpiles, according to public estimates.

Two Defense Department officials, who spoke on condition of anonymity, say they are vigilantly gathering intelligence on Russian military moves for any sign that it might be taking such weapons out of storage or preparing for deployment units trained in nuclear or chemical warfare.

‘Raising the ante’

Longtime observers of Russian nuclear policy have been startled at how reckless the Putin regime has been with its nuclear threats compared to leaders in Moscow during the Cold War.

“The communist party of the Soviet Union was incredibly disciplined about this,” said Rose Gottemoeller, a former undersecretary of state for arms control who has negotiated treaties with Russians and served as NATO deputy secretary general from 2016 to 2019. “There were only a few Soviet leaders who were allowed to speak about nuclear doctrine and strategy, and they did so in a very carefully scripted way.

“We are in a more difficult crisis than anyone could have predicted with this constant nuclear saber-rattling that has been going on,” she added. “We have to take what [Putin’s] people say seriously, because he was serious about invading Ukraine when many of us hoped he would turn away at the last minute.”

The dearth of diplomacy and growing distrust only fuels the risk of “mushroom clouds appearing on the battlefield,” Izumi Nakamitsu, United Nations high representative for disarmament affairs, warned on Tuesday.

She hearkened back to the numerous instances during the decades-long standoff between the United States and then-Soviet Union when the two sides nearly came to nuclear blows. But diplomacy — and a good bit of luck — prevailed.

“We are all aware of the close calls and near-misses,” she said at an event hosted by The Stimson Center. “Unfortunately, I fear we have forgotten many of those difficult lessons. A simple glance at a headline today can point to how acute nuclear risks have become."

Those concerns are shared across the spectrum by advocates for nuclear disarmament and those who believe a more robust U.S. nuclear arsenal is needed to deter adversaries.

“I really am worried here that the war is going so badly for Putin … it raises the possibility of Putin feeling like he needs to escalate to win his way out of this conflict,” said Tim Morrison, a former Trump White House nuclear policy adviser who is now a researcher at the Hudson Institute, a hawkish think tank.

That, he continued, “is right in the wheelhouse of Russian [military] doctrine for a low-yield nuclear or even chemical [weapons] use.”

Morrison added that he fears the situation could unravel to the point where Putin is “raising the ante, climbing the rungs of the escalation ladder to make the point to NATO ‘hey, you guys really need to knock it off with arming the Ukrainians, I will no longer tolerate this.’”

Russia has already ratcheted up the war with its hypersonic missile launch in Ukraine last week, and it has also been accused of dropping phosphorus bombs, which are banned under the Geneva Convention (though using the chemical to obscure troop movements or illuminate targets is not).

NATO Secretary General Jens Stoltenberg said on Wednesday the alliance will be assisting Ukraine with specialized equipment in the event of a Russian attack with chemical, biological or nuclear weapons.

Gottemoeller said she fears that Moscow’s use of a tactical nuclear weapon is a serious possibility. “Putin is capable of anything,” she said. “He could declare there is an existential threat from a NATO ally resupplying the Ukrainians.”

‘You’re not going to necessarily know’

Others worry less about Putin ordering a nuclear attack and more about a miscalculation leading to the use of nuclear weapons.

Nunn has been sounding the alarm about the threat of an accidental nuclear exchange as a result of a cyber attack on nuclear command-and-control systems — including by malign actors not directly involved in the conflict who could be confused for a nuclear adversary.

“Third parties, third countries, might interfere in terms of command-and-control or warning systems,” he said of potential hackers. “Interference in command-and-control could be taken in this kind of atmosphere as probably a deliberate act.”

Nunn successfully lobbied Congress last year to require the Pentagon to conduct a “failsafe review” of the U.S. nuclear arsenal “to prevent cyber-related and other risks that could lead to the unauthorized or inadvertent use of nuclear weapons as the result of an accident, misinterpretation, miscalculation, terrorism, unexpected technological breakthrough, or deliberate act.”

Further complicating the task of U.S. and allied commanders to decipher Russian intentions, said Morrison, is the fact that so many Russian battlefield systems are also designed to unleash both conventional and nuclear or chemical warheads.

In other words, it could be exceedingly difficult to know when the Russian military has decided to pursue a nuclear option.

“One of the problems with Russian nuclear forces is how many of their systems are dual-capable,” Morrison said. “So you’re not going to necessarily know if the S-300 or that long-range [missile or artillery] battery is packing a conventional warhead or a nuclear one.”

If U.S. military leaders detected Russian nuclear maneuvers, Nunn said, Biden may have no choice but to act more aggressively to deter Moscow, including putting American nuclear forces on alert.

“If you’d seen bombers in the air, all sorts of activities in the nuclear forces, it would have been a different proposition,” Nunn said. “The risk of nuclear use is in my view higher through a mistake or blunder than through intent. But nevertheless blunders get more likely when nuclear weapons are put on alert.”

The Nuclear Threat Initiative last week outlined a hypothetical but horrific scenario to underscore how the war in Ukraine could go wrong. In a simulation based on historical examples, the current conflict escalated with the detonation of a nuclear weapon in Ukraine and quickly spiraled into a nuclear holocaust.

The scenario lays out a chain of events — the downing of an American spy plane by accident, the misreading of counter actions, cyber attacks that further sow confusion, and leaders with very little time to react — that result in the unthinkable: an all-out nuclear war between the United States and Russia.

“Over the course of the next hour,” it chillingly details, “82 million Americans are killed with allied countries faring similarly. Most die instantly, while more will die of radiation poisoning over the coming days and weeks.”

‘The most imperative arms control’

There is also nearly uniform agreement that any glimmers of hope that the Biden administration might reach further agreements with Putin to rein in nuclear armaments have been dashed.

“Prospects of renewed arms control are very low,” said Nikolai Sokov, a senior fellow at the Vienna Center for Disarmament and Non-Proliferation who worked on arms control agreements in the Soviet and Russian foreign ministries.

He said one reason is now very personal. He believes a renewal of nuclear talks would likely require a summit between Biden and Putin, or at least their top diplomats, Secretary of State Antony Blinken and Foreign Minister Sergei Lavrov.

“By calling Putin a war criminal,” Sokov said, “Biden closed off the prospect of a summit, whether in person or a call. Same for Blinken-Lavrov. These things will stand in the way and, at best, delay arms control.”

But some who support nuclear disarmament say the Ukraine crisis only strengthens their argument for why these weapons are destabilizing and steps must be pursued to eliminate them around the world.

“Advocates for nuclear weapons have long argued that they keep the peace, acting as a stabilizing force,” said Stephen Young, the senior Washington representative for the Union of Concerned Scientists. “Putin is turning that belief on its head, using the threat of nuclear war to deter others from intervening against his forces in Ukraine”

“In other words,” Young added, “Russia’s nuclear weapons are enabling this war.”

He lauded Biden’s efforts at nuclear deescalation in the face of Putin’s threats. “But it isn’t enough,” Young said. “The president should take nuclear weapons off the table, and make clear that the sole purpose of U.S. nuclear forces is to deter or respond to a nuclear attack on the United States or its allies.”

Such dramatic changes to undo decades of American nuclear policy, which the Biden administration was not expected to make even before the Russian invasion of Ukraine, are widely viewed as more remote than ever given the current crisis.

‘A serious confrontation

For now, Nunn believes the most urgent task is to find a way to stop the shooting in Ukraine.

“The ceasefire is in my view the most imperative arms control right now," he said in an interview. “If we do not have a ceasefire, escalation becomes more likely."

He recently organized a joint declaration by former U.S. and European leaders, including one of Putin’s ex-foreign ministers, Igor Ivanov, calling for an immediate ceasefire in Ukraine.

They highlighted the recent firefight at the Zaporizhzhia nuclear power plant as a reminder of “how nuclear catastrophe can quickly rise to the surface in the ‘fog of war.’”

“The first and most essential step toward reducing the risks of a consequential accident, mistake, or miscalculation is a ceasefire to end the unacceptable and unjustifiable loss of human lives, including innocent civilians,” they wrote.

But Sokov said he worries that even with an end to the current hostilities, the nuclear stakes will remain historically high, especially if Putin believes his regime is at stake.

“I expect the post-war settlement to be a more dangerous period than the war itself,” Sokov said in an email. “It is pretty clear that the U.S. will not remove sanctions. In that situation, Moscow may conclude that reliance on nuclear weapons is the only means of avoiding the fate of Iraq, post-Saddam.”

That is “all the more so,” he added, “since its conventional forces will have been depleted and not judged efficient after the war. I expect a serious confrontation with a strong nuclear component.”