Here are the nuclear weapons Russia has in its arsenal

“This is not a bluff,” he warned the West. “And those who try to blackmail us with nuclear weapons should know that the weather vane can turn and point toward them.”

What if Putin isn’t bluffing? What sort of nuclear strike is Russia, the country with the world’s largest stockpile of nuclear weapons, capable of — and what kind of destruction might it wreak in Ukraine and beyond?

“Nuclear weapons, they’re unlike any other weapon,” said Joe Cirincione, a nuclear weapons expert who previously served as president of the Ploughshares Fund. “And that’s just the explosive part — not to mention the thermal effects and the temperatures that are produced.”

It is very unlikely that Russia would use its most powerful nuclear weapons to settle scores with Kyiv; Moscow is far more likely, experts agree, to use a smaller nuclear weapon in the hopes of achieving a specific battlefield objective. But, those same experts caution, once a nuclear weapon is unleashed, controlling what happens next is difficult.

“Once you start talking nukes, all bets are off,” said Hans Kristensen, the director of the Nuclear Information Project at the Federation of American Scientists. “So it’s not clear how far this will go.”

How many weapons?

The first and most basic question about the Russian nuclear arsenal is: How many of the weapons does Russia have? It is a difficult one to answer.

Nuclear weapons are commonly divided into two categories: strategic weapons — those being the longer-range missiles that can cross oceans and threaten rival superpowers — and tactical weapons, those that have a more limited capacity and arguably could serve a more limited function.

The United States has a good count of Russia’s strategic weapons, because Washington and Moscow are required to disclose this under the terms of New START, the last remaining arms control treaty. That count of strategic weapons is split among those deployed on intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs) and those launched from bombers.

But when it comes to the tactical weapons, the U.S. intelligence community can only offer its best guess, and different agencies have differing estimates. The ballpark figure they have settled on is between 1,000 and 2,000 tactical weapons (which, it should be noted, can be launched from ground launchers, ships and bombers but are not pre-deployed). After careful study, the Federation of American Scientists put its estimate at 1,912 — although it cautions that this could include weapons being retired or taken offline.

How powerful are these weapons?

The power of a nuclear weapon is its yield, and yield is measured as a TNT equivalent. The U.S. Department of Energy estimates that the American bombs that were dropped on Hiroshima and Nagasaki had yields of 15 and 21 kilotons, respectively — so equivalent to 15,000 tons and 21,000 tons of TNT.

Modern strategic nuclear weapons have enormous power. Standard ones can have yields of 500 kilotons, 800 kilotons and even 1 megaton — equivalent to 1 million tons of TNT. Russia holds the record for the most powerful weapon ever exploded: In 1961, it tested a bomb of at least 50 megatons, nicknamed “Tsar Bomba” — or the tsar of all bombs.

Modern tactical weapons usually have a capacity of 10 to 100 kilotons, which still makes the average tactical weapon potentially more destructive than the bombs used on Hiroshima and Nagasaki. Russia and the United States also have “low-yield” nuclear weapons that pack a “light” punch, even dipping below 1 kiloton. But even the least-powerful nuclear bomb — with a yield of about 0.3 kilotons — has about the same explosive power as the 2020 Beirut port explosion.

What weapons would Russia be most likely to use?

Russia has various kinds of tactical nuclear weapons. Some are designed for use by the navy, some to be used by the air force and others to be used by the army, either in surface-to-surface short-range missiles or in surface-to-air air defenses. The yield varies by purpose, since it takes more power to penetrate, say, an underground bunker than it does to stop an incoming warplane.

Russia has different-size stocks of all these weapons. For example, the Federation of American Scientists believes Russia has about 500 tactical air force nuclear weapons, a figure that includes gravity bombs and air-to-surface cruise missiles. Many of those would be delivered by aircraft that we have seen on conventional bombing missions in Ukraine. These planes include the Tu-22 “Backfire” bomber that Russia has used to strike central Ukraine and the Su-34 “Fullback,” one of which Ukraine claimed to have shot down last month. But experts do not think the Russians are necessarily going to use those.

A far more likely candidate is the 9K720 Iskander missile system, classified by NATO as the SS-26, which is a ground-based ballistic missile. But according to Kristensen of the Federation of American Scientists, there are far fewer of these in Russia’s arsenal — only about 100 weapons. So why would Iskander be the nuclear delivery system of choice?

“Simply because it’s the most reliable, and the one that would have the best chance of making it to its target,” Kristensen said. “Not being shot down, not failing.”

How much destruction can these weapons cause?

The first metric to pay attention to when estimating the destructive capacity of a nuclear weapon is its yield. If the kilotons number is bigger, the blast is going to be bigger, all else being equal. But all else is usually not equal. Terrain can be a factor — if there are hills in the area of the blast, they can buffer some of the radiating effects of the blast. If the target and the blast occur underground, the ground itself can absorb some of the blow. And whether the weapon is detonated on a surface or a just above the surface can also make a huge difference.

There are also the radiation, radioactive debris and long-term poisoning affects to worry about. But according to Kristensen, there are ways to avoid this impact if people in the blast area take proper shelter, which may not be available in a war zone.

“If you go down in your basement and you stay there with your ventilation system turned off for three to four days, then most of the acute radiation will have disappeared, so that you’re able to at least go out,” he said. But while people might be able to breathe more easily at that point, they will still have to make sure their food and water supply haven’t been compromised.

Will there be a warning?

History and Hollywood have instilled in our imaginations the image of world leaders with their fingers hovering over a big nuclear button, just one false flinch or sneeze away from lighting the world on nuclear fire. While the major strategic weapons can be launched within minutes of an order being given, that is not the case for Russia’s tactical weapons.

Those weapons are stored at a limited number of facilities around the country, from which they have to be removed and transported. That process takes days, according to the experts. And those movements would probably be detected by U.S. and European intelligence services.

They will be watching for things like the mobilization of military units that aren’t usually active; an increased presence of strategic forces; and more trucks or trains appearing to move toward Ukraine from the locations where officials know such weapons are stored. In recent days, reports of armored train cars moving through central Russia caused a stir and some worried they were witnessing the first sign of a nuclear attack. But so far, the experts aren’t flinching.

“Read that with an enormous grain of salt, because there are also all sorts of reasons for why the vehicles could be on those trucks,” Kristensen said, noting that U.S. intelligence agencies were strikingly quiet — which would not be the case if a nuclear attack on Ukraine were imminent.