Will Putin Use Nuclear Weapons? Watch These Indicators.

I asked several experts to share the indicators they’re tracking most closely to determine whether Russian nuclear use in Ukraine is imminent—and to help us all separate the signal from the noise.

Collage of showing cropped pictures of Putin overlapping the radiation symbol
Antonio Masiello / Getty; The Atlantic

If Vladimir Putin were to decide to use nuclear weapons in Ukraine, would we know ahead of launch? If so, how exactly would we know?

Not since the early days of the war in Ukraine have these questions felt so urgent. As Putin has suffered battlefield setbacks and illegally annexed Russian-occupied territory in eastern Ukraine, he has repeatedly threatened to make use of his country’s nuclear weapons—appearing to implicitly extend the protection of Russia’s nuclear arsenal over lands that Ukrainian forces could soon seek to retake. U.S. officials have underscored the gravity of the situation as well; President Joe Biden recently traced a direct line from what he deemed the serious risk of Putin going nuclear to “Armageddon.”

In these circumstances, feeling on edge is only natural. But in reporting on nuclear threats over the years, I have learned the pitfalls of assigning undue weight to rhetorical shiny objects. In 2017, for example, when Donald Trump and Kim Jong Un were calling each other “Little Rocket Man” and a “mentally deranged U.S. dotard” and warning of all manner of nuclear apocalypse, experts advised me to peer past the bombast and look for clues of impending war, such as the evacuation of American noncombatants from South Korea. Those clues never materialized. Nor did the apocalypse.

In a similar spirit, I asked several experts to share the indicators they’re watching most closely to determine whether Russian nuclear use in Ukraine is imminent—and to help us all separate the signal from the noise.

“I do believe that we are at least several steps away from” Russian nuclear use in Ukraine, Pavel Podvig, an expert on Russian nuclear forces, told me.

Below is a breakdown of what those remaining steps could look like.

A shift to more explicit, specific nuclear threats by Putin and other Russian officials

Despite Putin hinting recently that threats to Russian “territorial integrity” could spur the Kremlin to use nuclear weapons, Podvig maintained that the Russian president and other top officials have nevertheless largely been consistent in articulating a defensive doctrine, in which the Russian government would consider using nuclear weapons only if it were to sustain an attack that threatened the existence of the Russian state.

Podvig is looking out for a shift away from that doctrine, which could involve Russian leaders more explicitly threatening to use nuclear weapons to halt Ukrainian advances on the battlefield. Matthew Kroenig, a nuclear strategist and my colleague at the Atlantic Council, served up a scenario: Imagine that Putin, seeing the lands he recently annexed about to slip from his grasp, declares, “‘I warned the world that these four regions are Russian territory. I warned Ukraine not to attack Russian territory. They’ve not heeded these warnings. They need to evacuate these areas immediately, or else I’ll consider nuclear weapons. This isn’t a bluff.’” That’s the kind of more specific statement that would put Kroenig on higher alert.

“We will know it when we see that,” Podvig said of a possible rhetorical shift. “My take is that, so far, we haven’t seen it.”

A definitive rout of Russian forces in Ukraine and corresponding threats to Putin’s power at home

As a dictator who controls the media, Putin could spin any partial Russian win in Ukraine as a victory, Kroenig reasoned. But if Ukrainians are on the verge of taking back all of their territory, Putin could conceivably turn to nuclear weapons to reverse his military misfortunes and avoid a humiliating defeat.

Kroenig, who served in the Department of Defense and the intelligence community in the Bush, Obama, and Trump administrations, is relatedly tracking “Putin’s strength at home,” because “if we saw more Russian elites turning against him or publicly criticizing him,” Putin “could seek nuclear use as a way to gamble for resurrection, change the conversation, [and] show that he’s a strong leader.”

This is one of the core conundrums in this confounding war: The United States and its partners are rightly supporting Ukraine’s campaign to regain all the territory it has lost to Russia’s illegal and abhorrent aggression. But investing in Ukraine’s unequivocal success, and thus Putin’s utter defeat, may come with the greater risk of a desperate Putin unleashing nuclear war.

Movements of Russian tactical nuclear weapons from storage to the field

The general consensus among experts is that if Putin were to reach for his nuclear weapons in the course of his war in Ukraine, he wouldn’t select the kind of long-range, city-destroying, “strategic” nuclear weapons that were so prominent during the Cold War. Instead, he’d likely opt for one or several of the country’s roughly 2,000 tactical nuclear weapons—less explosive, shorter-range arms intended for use on a battlefield.

These tactical nuclear weapons are not deployed and ready for immediate use the way that Russia’s ground- and sea-based strategic nuclear weapons are. Experts believe they are held in an estimated 47 national and base-level storage facilities across Russia. The country’s systems for launching these weapons are stashed away in separate locations.

Podvig has sketched out how a move to tap into this arsenal could play out. In the event of an order to raise Russia’s state of readiness, the defense ministry’s 12th Main Directorate, the custodian of the country’s nuclear arsenal, would remove the selected weapons from storage and put them on specialized trucks, which would bring them to a designated point where they would be taken out of their storage containers and paired with their delivery systems (loading a nuclear bomb onto an aircraft at an air base, for instance, or installing a nuclear warhead on a missile).

Through its satellites, other surveillance capabilities, and various forms of on-the-ground intelligence, the U.S. government would probably (not certainly) be able to spot signs of Russian efforts to move tactical nuclear weapons out of storage facilities.

Private researchers poring over open-source intelligence would, conversely, be less likely to catch this activity. But the broader public might quickly find out about it anyway. Just as it did in novel ways in the lead-up to the war in Ukraine, the Biden administration might disclose classified intelligence—through either leaks to the media or public statements—to expose Putin’s plans and marshal international pressure, including from more Russia-friendly nuclear-armed states, such as China and India, as a means of deterrence.

In such circumstances, “I think President Biden and other officials would”—publicly and privately—“signal very aggressively to the Russians to dissuade them from escalating the conflict with nuclear weapons,” Jeffrey Lewis, a nuclear-nonproliferation expert at the Middlebury Institute of International Studies at Monterey, told me.

The experts I consulted also agreed that Putin himself would probably want to telegraph to the world in subtle or blatant ways that he’s making these moves—in part because he could never be fully confident of taking these steps without his adversaries detecting them, but also because, as Lewis put it, he would want “to see if he could get what he wants for free.”

If Putin can “frighten” Ukraine’s allies into standing down without actually using nuclear weapons, “that’s the best outcome for him,” Kroenig said. Kroenig could even envision the Kremlin “ostentatiously” recording video of Russian troops removing tactical nuclear weapons from storage facilities and Putin deliberately leaking it, with a message to the world like “‘We’re moving them to the front lines. We’re getting ready to use them. I’m serious. Back off now, or else this is coming.’”

Intercepted communications suggesting forthcoming nuclear use and corresponding movements of Russian forces or military assets

If Russia were preparing to use nuclear weapons, Podvig said, it would likely “raise the level of readiness of a portion of forces,” which “generates a certain footprint,” such as orders and additional communication through both Russia’s nuclear command-and-control system and other military channels. Russia has practiced these processes during past military exercises, so the U.S. government has a sense of the patterns to watch for. One recent assessment estimated that “tens of thousands” of Russian soldiers would ultimately need to be involved in the complex logistical operation of transferring tactical nuclear weapons from storage to the battlefield.

“I would expect to see alert levels rise throughout Russia’s nuclear forces before any nuclear use, no matter how small,” Lewis said, particularly because the country’s generals will need to gird those forces for escalation that could result from any U.S. or NATO retaliation following Russian nuclear use. Moving Russian nuclear forces to a higher state of readiness could involve not just activity at storage sites for nuclear warheads, but also “submarines going out to sea” or “mobile missiles leaving their bases.”

Although open-source researchers such as Lewis don’t yet have the capabilities to monitor Russian communications, here, too, the U.S. government could choose to publicly release any intelligence it gathers on Russian military orders that signal nuclear use is in the offing.

A particular challenge with reading the Kremlin’s tea leaves is that Russia has nearly two dozen “dual use” delivery systems, some already being used in the war in Ukraine, which can carry conventional or nuclear warheads. U.S. intelligence could “assume they have conventional warheads on them, but actually they don’t,” because Putin has “switched them out somewhere and we didn’t detect that,” Kroenig noted. “So it is possible, I guess, that we just start seeing mushroom clouds in Ukraine, but I think that’s less likely than that we’d get some kind of warning.”

In recent weeks, U.S. and allied officials have repeatedly stated that they have not detected signs of imminent Russian nuclear use. And the experts I consulted mostly concurred, although Kroenig noted that because Putin is beginning to lose the war and sharpen his threats, “we are already in the danger zone.”

“There is always some background level of activity with [Russia’s] nuclear forces,” as there is in any nuclear-armed country, Lewis noted. But so far, he has “not seen anything in Russia” that he “would characterize as unusual.”

When I asked Podvig whether he’d seen any of his top indicators for looming Russian nuclear use, he hesitated and then replied, “Not yet.” A message of great reassurance this was not. But I’ll take it over the latest runaway speculation on Twitter.