This week, NATO is conducting its regular, long-planned nuclear strike exercise known as “Steadfast Noon” to practice deploying fighter jets used to carry nuclear weapons. And Russia is expected to conduct its own nuclear drills sometime this month—as it typically does—in reaction to NATO’s exercises.  While these rehearsals don’t involve actual bombs, they come at a fraught moment, given Russian president Vladimir Putin’s recent suggestion that the Kremlin could deploy nuclear weapons in its war against Ukraine. 

Officials from the United States and the United Kingdom have emphasized that they do not see indications that Russia is actively preparing to launch a nuclear strike. And the signals the global community has to draw on in monitoring the Russian nuclear weapons program, while not infallible, are robust. That means the world would likely know if a nuclear attack were imminent.

 “We take any nuclear weapons or nuclear saber-rattling very seriously here,” White House press secretary Karine Jean-Pierre told reporters earlier this month. But, she added, “we have not seen any reason to adjust our own strategic nuclear posture, nor do we have any indication that Russia is preparing to imminently use nuclear weapons.”

Similarly, Jeremy Fleming, director of the UK’s GCHQ intelligence agency, said last week, “I would hope that we will see indicators if they started to go down that path.” He added that there would be a “good chance” of detecting Russian preparations.

“With Russia, the arsenal is old and established, much like the US’s nuclear weapons program,” says Eric Gomez, a senior fellow at the Cato Institute focused on arms control and nuclear stability. “Russia is very much enmeshed in the international and bilateral arms control treaties that provide a lot of transparency. They’re not an open book—no country is. Everyone still has certain secrets that they preserve. But if you can keep satellite or aircraft sensors trained on key spots, you can catch it if things are moving or dispersing.”

As is the case in the US and among other world nuclear powers, Russia’s intercontinental ballistic missiles and submarine-launched ballistic missiles are always deployed and in a constant state of readiness. Known as “strategic” nuclear weapons, these bombs are meant to target cities or large industrial targets—probably what you think of when you imagine a nuclear bombing. The “tactical” nuclear weapons that are of more immediate concern in a Russian strike on neighboring Ukraine are smaller and meant for more contained attacks, namely in battle zones. These bombs are also known as “battlefield” or “nonstrategic” nuclear weapons and have never been used in combat.

Russia’s nuclear bombs are stored in military facilities and would need to be transported and loaded into either aircraft or launchers for deployment. Pavel Podvig, who runs the research organization Russian Strategic Nuclear Forces, notes that the global community knows the location of the roughly 12 nuclear weapons storage facilities around Russia where this activity would likely originate. He adds that the US has intimate knowledge of most of the sites because it worked with Russia to improve the physical security of the repositories between 2003 and 2012 as part of an initiative called Cooperative Threat Reduction.