BLOOMINGTON – The ebbs and flows of the war in Ukraine still manage to command headlines these days, even if it’s without the intensity of previous months. But for all the attention to the battles and maneuvering on the ground, the issue that keeps US policy makers up at night shows up only infrequently: Russia has the world’s largest nuclear arsenal (in terms of numbers of warheads), and no one in the West really knows whether its military would use it, how they’d deploy it, and under what circumstances they’d take that step.

As CIA Director Nicholas Burns made clear back in April, the issue is the use of so-called tactical – or “low-yield” – nuclear weapons. “None of us can take lightly the threat posed by a potential resort” to them, he told reporters. Still, he added, “While we’ve seen some rhetorical posturing on the part of the Kremlin about moving to higher nuclear alert levels, so far we haven’t seen a lot of practical evidence of the kind of deployments or military dispositions that would reinforce that concern. But we watch for that very intently, it’s one of our most important responsibilities at CIA.”

Let’s be clear that “low-yield” is a matter of degrees. By current standards, at 15 kilotons the bomb dropped on Hiroshima was a “low-yield” weapon. These weapons contain such awesome destructive power that even a minor nuclear explosion would be devastating.

So even if there’s no evidence at the moment that the Russians intend to deploy their tactical nukes, as a matter of policy the US and our allies need to remain constantly on the alert for any signs of their potential use. As Burns said early in May, Russian President Vladimir Putin is “in a frame of mind in which he doesn’t believe he can afford to lose.”So we have to be very clear that any use of these weapons is unacceptable and exceedingly dangerous. Russia has plenty of problems on its plate and it’s unclear whether it has the forces, the time, or the will to expand the current conflict – but the West must be very plain that it would push back hard on any escalation.

During the 2020 presidential campaign, Joe Biden pledged to declare that the US would use nuclear weapons only to deter a nuclear attack on us or our allies. His administration’s approach, revealed in March, declared, “As long as nuclear weapons exist, the fundamental role of U.S. nuclear weapons is to deter nuclear attack on the United States, our allies, and partners,” but continues a longstanding policy that leaves open the option of using nuclear weapons to respond to non-nuclear threats, such as the use of biological or chemical weapons.

If you find thinking about these kinds of scenarios as unsettling as I do, then you might agree that – along with the impact of climate change – by far the largest threat to the stability of the world is the threat of nuclear weapons and their proliferation. Yet perhaps because the possibility of their use seems so remote in our day-to-day lives, you don’t see much about it – in the press or as an agenda topic in Washington. Policy debates don’t pay much attention to it, Congress doesn’t seem especially engaged with it – as Nicholas Burns suggested, it’s a behind-the-scenes preoccupation for people whose job it is to pay attention. I’d suggest that we all need to pay more attention – a lot more.

What the war in Ukraine makes clear is that anytime there’s a conflict involving a country that possesses nuclear weapons, the world edges closer to the possibility of their use. Although there is considerable discussion now about climate change, the public discussion of the threat of nuclear weapons is by comparison very limited. They are equally strong threats, and should be getting comparable amount of attention and discussion. 

The last time they were deployed in a conflict was almost 80 years ago, thanks to the hard work of countless people working for governments and non-governmental organizations around the globe. But we’ve also been lucky, and there’s never a guarantee that luck will hold. Vladimir Putin’s sabre-rattling is an opportunity and a spur to take a fresh look at what more needs to be done to ease the threat that nuclear weapons pose to world stability. 

Lee Hamilton is a Senior Advisor for the Indiana University Center on Representative Government; a Distinguished Scholar at the IU Hamilton Lugar School of Global and International Studies; and a Professor of Practice at the IU O’Neill School of Public and Environmental Affairs. He was a member of the U.S. House of Representatives for 34 years.