Putin's nuclear threats are stirring fears of a nightmare scenario. Here's what's in his arsenal and what could happen if he orders the unthinkable.

Russian soldiers stand near a Topol-M ICBM while participating in a rehearsal for the nation's Victory Day parade outside Moscow. ALEXANDER NEMENOV/AFP via Getty Images

• Putin has repeatedly made nuclear threats since he launched Russia's invasion of Ukraine.
• Experts say the immediate risk of a nuclear attack is low, but they are growing increasingly concerned.
• The use of a nuclear weapon is "directly tied to Russia's fate on the battlefield," one expert recently told Insider.

Russian President Vladimir Putin has made a lot of very unsettling nuclear threats since the start of Russia's unprovoked war in Ukraine, and concerns are growing as his forces lose ground that he could resort to the unthinkable and order the use of weapons of mass destruction, a nightmare scenario.

The day Putin launched his so-called "special operation" in Ukraine in late February, he said that "Russia remains one of the most powerful nuclear states" and warned that any enemy that attacks it "will face defeat and ominous consequences."

Putin, who claimed to have placed Russia's nuclear deterrent forces on high alert just days later, has continued to remind the world of Russia's nuclear might in the months since.

In September, Putin made a veiled reference to nuclear weapons while vowing to defend Russia's "territorial integrity," emphasizing that "this is not a bluff." And later that month, Putin said that the use of nuclear weapons by the US against Japan in World War II set a "precedent" as he warned that "we will protect our land with all the forces and means at our disposal."

World leaders and international institutions have criticized Putin over his repeated threats, accusing him of nuclear saber rattling. In August, UN Secretary-General Antonio Guterres warned that the world is "one misunderstanding" away from "nuclear annihilation."

President Joe Biden recently went as far to suggest the risk of nuclear "Armageddon" is the highest it's been since the 1962 Cuban Missile Crisis, and the US has privately communicated to Russia that there would be "catastrophic consequences" if nuclear weapons are used. 

Though some Russia watchers suspect Putin is bluffing to deter Western support for Kyiv, many top nuclear experts say that his threats should be taken seriously regardless.

Russia's tactical and strategic nuclear weapons

A Russian Iskander-E missile launcher on display at the International Military Technical Forum 'Army 2022' on August 17, 2022 in Patriot Park, outside of Moscow, Russia. Getty Images

Putin, who has issued threats in vague terms, has not expressly said whether or not or how he might use a nuclear weapon, but military and nuclear weapons experts have said that if he did, Putin is more likely to employ a tactical nuclear weapon in Ukraine than a strategic nuclear weapon, though the latter remains an option.

Tactical or non-strategic nuclear weapons are meant for more limited strikes or use on the battlefield over a shorter range while strategic nuclear weapons typically have higher explosive yields and are intended to be used against targets farther from the front lines.

Russia has the largest nuclear stockpile in the world with 5,997 warheads, though roughly 1,500 are retired, according to the latest assessment from the Federation of American Scientists, and not all of Russia's active nuclear weapons are deployed.

Russia is estimated to have around 1,912 tactical nuclear weapons in its arsenal, and it maintains a fully operational nuclear triad, giving it the ability to deliver nukes to their intended targets by way of land, air and sea.

The explosive yield of a tactical nuclear weapon tends to range from around 10 to 100 kilotons (a kiloton is a unit of measurement equivalent to the explosive force of 1,000 tons of TNT), but Russia also has low-yield nukes that fall below one kiloton.

That said, these weapons are still extraordinarily powerful. The atomic bomb dropped on Nagasaki by the US during World War II had an explosive yield of just 21 kilotons, but it killed roughly 140,000 people. There are tactical nuclear weapons that are more than four times as powerful. 

"These are devastating and indiscriminate killing machines," Daryl Kimball, executive director of the Arms Control Association (ACA), said of tactical nuclear weapons during a Tuesday webinar hosted by his organization. 

A Russian Yars RS-24 intercontinental-ballistic-missile system drives during a rehearsal for the Victory Day parade in Red Square in central Moscow, Russia, May 7, 2015. REUTERS/Grigory Dukor

Demonstrating resolve by going nuclear

Pavel Podvig, a senior researcher at the United Nations Institute for Disarmament Research, does not believe that at this stage, despite Putin's rhetoric, Russia is close to breaking the atomic taboo, potentially alienating its remaining allies and entrenching its status as an international pariah.

And "there is a consensus among people who've been looking at all this that the battlefield use of nuclear weapons is very much out of the question," Podvig told Insider from his home in Geneva. "This is not that kind of war."

Ukraine's forces are dispersed, meaning there likely would not be an opportunity to take out thousands of soldiers in a strike. At best, a single tactical nuclear weapon could destroy about a dozen tanks, Podvig said. It would also, among other things, be a logistical nightmare for a military that at least early on struggled to even feed its own troops.

"You need to coordinate. You need to deal with all the contamination," he said. "It's not easy."

Even if the intent of such a strike were to simply demonstrate Russia's resolve and willingness to escalate, Podvig does not think it would achieve that with a battlefield nuke — it could in fact be read as Moscow being hesitant. If the Kremlin were seeking an effective demonstration, he argued, "it would have to be shocking," like nuking an entire city.

"It won't be enough just to have an explosion over the Black Sea somewhere to deliver the shock. You really would have to kill a lot of people — we are talking about tens, maybe hundreds of thousands of people," he said. "And you would have to do that very much in cold blood."

The devastation caused by a nuclear weapon could undermine Putin at home though. He sold this conflict to his population on the basis of shared history with Ukraine, creating a potential backlash were he to oversee, by way of nuclear force, the destruction of cities or the mass killing of Ukrainians, who he has described as "one people" with Russians. Such sentiments, however, have not prevented other wartime atrocities.

It's Putin's call whether to use a nuke

Russian President Vladimir Putin and top officials during a meeting with former members of the Cabinet at the Kremlin on January 29, 2020 in Moscow, Russia. Mikhail Svetlov/Getty Images

Russia released a document in 2020 called the "Basic Principles of State Policy of the Russian Federation on Nuclear Deterrence," which outlines its nuclear doctrine. The document states that the Russian president makes the decision to use nuclear weapons.

"The Russian President is the Supreme Commander in Chief of the Russian Armed Forces, and he has the authority to direct the use of nuclear weapons," per the Congressional Research Service. 

In other words, it's Putin's call whether Russia uses a nuke, but letting one loose is not as simple as the press of a button.

If Putin ordered a nuclear strike, it's possible that at some stage his orders could be refused. But there's no way of knowing if anyone would dare stand against the Russian leader, whose opponents have a history of winding up in prison or dying in violent ways. 

The whole process starts with a decision by Putin, Hans M. Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, explained during the ACA webinar on Tuesday. "But of course, like in the United States, the military has to cooperate," he said.

"I don't think there's a red button on his desk that he can press and then suddenly the nuclear weapons start flying," Kristensen said, and it would likely "take longer," he continued, to use a tactical nuclear weapon than a strategic one given that these weapons are not immediately available.

Russia's non-strategic nukes are "in central storage and would have to be brought out of their bunker first and transported out to the launch units that would fire them," Kristensen explained, adding that it's "reasonable to assume" Western intelligence would detect whether this is occurring given the number of steps involved. US intelligence has so far seen no indication that Putin is preparing to use nuclear weapons, according to recent reporting.

And some of these nukes are potentially unreliable given their age and time in storage.

"Most of these warheads stored there are very old," Pavel Baev, a military researcher who previously worked for the Soviet defense ministry, recently told the Guardian. "Without testing it's really hard to say how suitable they are because many of them are past their expiration date."

Putin's nuclear calculus

Russian President Vladimir Putin Contributor/Getty Images

The document released by Russia in 2020 lays out four scenarios that could potentially lead to the use of nuclear weapons: the use of nuclear weapons or weapons of mass destruction against Russia or its allies, conventional aggression that threatens Russia's existence, ballistic missiles that are already in flight and heading for Russia or its allies, and an attack on the government or military that jeopardizes Russia's nuclear response capabilities.

But Putin's recent threats suggest that he might, though the risk remains low, ignore Russia's official nuclear doctrine and use a weapon of mass destruction to send a grave message to Ukraine and its Western allies. 

There's an open, evolving debate over whether Putin would actually take the extreme step of using a nuclear weapon, but there's widespread agreement that the Ukraine war has raised the risk of a nuclear crisis to a level not seen in decades.

Kristensen said during the ACA webinar on Tuesday that he believes it's unlikely that Russia employs nuclear weapons in Ukraine. For that to happen, things would have to "escalate significantly" to a "direct clash between NATO and Russia," he said.

"That said, they've certainly rattled the sword and threatened something that looks like a scenario going beyond what Russia's declaratory policy is," he said, adding that if Russia did choose to use a nuclear weapon it would likely turn to a nuclear-armed Iskander short-range ballistic missile.

The risks of Putin employing a nuclear weapon in the short-term are "still low," Andrea Kendall-Taylor, a former senior intelligence officer who led strategic analysis on Russia for the National Intelligence Council from 2015 to 2018, told Insider in late September. But Kendall-Taylor also emphasized that Putin's decision to annex four Ukrainian territories — declaring territories on the front lines of the war as part of Russia — "increased those risks." 

"I do worry now that as the Ukrainians reclaim territory that Russia has now annexed and that [Putin] claims as Russian, given that he now is so personally invested in this, that the risk of his use of a tactical nuke on the battlefield in Ukraine has gone up," she said, going on to say that the use of a tactical nuclear weapon in Ukraine is "directly tied to Russia's fate on the battlefield."

Military and Russia experts widely agree that Putin will probably wait and see how his risky decision to announce a partial military mobilization plays out before he begins to seriously consider something as extreme as the use of a nuclear weapon.

In the meantime, Russia is more likely to engage in other escalatory steps — such as sabotaging infrastructure. Russia carried out strikes across Ukraine on such targets this week, attacking Kyiv for the first time in months in the process. 

If Putin did decide to use a tactical nuclear weapon in Ukraine, it would likely be "in hopes of shocking Ukraine into surrender or the West into cutting off aid to Ukraine," according to an assessment from the Institute for the Study of War. "Such attacks would be highly unlikely to force Ukraine or the West to surrender, however, and would be tremendous gambles of the sort that Putin has historically refused to take," ISW said.

Responding to the unthinkable

President Joe Biden and Russian President Vladimir Putin in Geneva, Switzerland. Mikhail Metzel/Getty Images

One of the most pressing questions surrounding the potential use of a nuclear weapon by Russia is how the West, and more specifically NATO, would respond. 

Ukraine is not a nuclear power. But multiple countries in NATO, a 30-member military alliance that has supported Ukraine in its fight against Russia, have nuclear arsenals of their own — including the US. 

The US and Russia collectively possess roughly 90% of the world's nuclear warheads. The two countries came dangerously close to nuclear war on more than one occasion during the Cold War, often by accident, but fortunately managed to avoid a catastrophe.

The Biden administration has warned Russia there would be serious consequences if nuclear weapons are used, but it has not gone into specifics. Experts advise not going nuclear in response.

"I do not believe that a nuclear response is something that the United States and its allies should be placing on the table. We need to stay on the side of perhaps a firm military response, but one that would stay conventional in nature," Rose Gottemoeller, a former senior State Department official for arms control and nonproliferation issues and former deputy secretary general of NATO, said during ACA's webinar. Gottemoeller said that the response could target where Russia's nuclear attack originated, but the US could also consider executing a non-lethal attack first, such as employing offensive cyber capabilities. 

"Any such attack would be carefully designed to be proportionate and to be responsive to what would be an egregious attack on a Ukrainian target using a nuclear weapon," Gottemoeller said, adding that she wanted "to stress and really underscore that none of these options for military action are desirable to NATO or to the United States of America."