Can Europe defend itself against a nuclear-armed Russia?

Many European leaders believe they can no longer rely on the U.S. for the high level of defensive support they have counted on for decades now that President Donald Trump, a longtime critic of NATO and the European Union, has returned to office.

In this edited conversation, Richard D. Hooker Jr., a senior associate at the Belfer Center’s Project on Europe and the Transatlantic Relationship at Harvard Kennedy School, discusses what Europe has to do to get ready for that new reality.

A distinguished veteran, Hooker served in national security roles during the Trump, George W. Bush, Bill Clinton, and George H.W. Bush administrations and had been on the faculty of National Defense University, National War College, and U.S. Military Academy at West Point.

---

You recently wrote that Europe has to shore up its own defense because it is no longer a priority for the U.S. How do things look at this moment?

I think for sure the threat to European security is much greater. The reason is the perception that the U.S. is disengaging and, in some ways, working with Russian President Vladimir Putin. That encourages Putin and dismays the Europeans, which has a downside and an upside.

The U.S. has worked for decades to suppress any notions of European strategic autonomy. We always thought we’d be the primary security provider in Europe, and we like being the leaders of NATO. So to that extent there’s been very halting progress at developing a separate or independent capability in Europe.

There’s an article in The Wall Street Journal that argues that Europe’s got way more in the way of forces and in wealth than Russia. But when you really peel the onion back, there are a lot of problems with that thesis.

The first is that readiness across Europe is quite low, even among the major powers — the French, the British, the Germans, the Italians. They would struggle to put a single army combat division in the field in less than 60 or 90 days. They probably could not put a second in the field for much longer after that.

The U.K. had 66 divisions in World War I, it would struggle to put one out in 90 days to defend the Baltic states. So that’s a pretty low level of readiness.

Why isn’t it more robust?

The militaries across Europe have gotten much, much smaller. In the last 30 years, they’ve gone to volunteer militaries, which are much more expensive, and you can’t generate reserves with volunteer militaries. And we’ve seen from Ukraine that modern warfare, no surprise, causes a lot of casualties and consumes a lot of resources. So that’s a problem.

But the real problem is what we call the enablers. It is all the below-the-line capabilities that enable you to actually fight. This is logistics, air defense, medical support, artillery at the corps level — those kinds of things. You just don’t find those in Europe.

And so, it’s really hard to put a force together that could deter or stand up to the Russian Federation in a major war because those capabilities are either absent or very much attenuated.

Now, the overarching issue for everything is, if the U.S. disengages and withdraws its nuclear umbrella, there’s really no answer in Europe for that. There just isn’t.

That would put the European nations, and particularly those in the east, under great, great pressure, because Putin would threaten to use tactical nuclear weapons, and there’s nothing to deter that. There’s no response other than the U.S. umbrella. And there are those who argue, even now, in practice, de facto, that umbrella’s been withdrawn.

“If the U.S. disengages and withdraws its nuclear umbrella, there’s really no answer in Europe for that.”

Is Europe correct to worry the U.S. nuclear umbrella has been withdrawn?

Has it been withdrawn already? I don’t know. Is it reliable? I wouldn’t think so.

If Putin were to threaten or actually use tactical nuclear weapons in Ukraine or, let’s say in Estonia, would the administration respond with nuclear threats of its own? Personally, I have my doubts. I worked in the first 18 months of the Trump administration. I was the senior NATO guy, which is not a comfortable job to have, and I have my doubts. I’ll just leave it at that.

What are Europe’s biggest defensive shortcomings, ones that hurt its strategic autonomy?

No. 1, of course, is the nuclear question.

No. 2 is they don’t really have higher level formations. They have a lot of corps headquarters, but they’re not real corps headquarters. They don’t have the artillery, the air defense, the engineers, all that stuff that you need to fight at the corps level.

No. 3 is the readiness of the formations they do have is quite low, so they can’t push out meaningful forces in 14 days the way the U.S. can.

It’s very easy to think of Europe as one entity, but it’s really not. It’s 44 different polities, and they all see the world a little bit differently.

The eastern flank countries, they all see the world the same. The Poles, the Baltic states, the Nordics, they all border Russia. They’re spending a lot of money; they’re going back to conscription; they’re getting better every day. They see the world the way it really is. All the other nations, not so much.

Do you think European leaders are genuinely motivated to take action?

I think it’s underway. I really do. But it’s not the kind of thing that you can solve overnight.

One clear sign is that defense spending continues to rise in many places. Not in every place in Europe — there are still some key states that don’t even make 2 percent. But the big ones have all said, “We’re going to work toward 3 percent,” and their budgets do seem to be rising.

Collectively, the Europeans hit the 2 percent target in 2024, and they have been increasing spending quite a bit over the last four or five years, but it hasn’t translated yet into actual capability.

So many people, even experts, just repeat this mantra that “the Europeans aren’t spending enough.” Actually, they spend more than four times more on defense than Russia does. Russia spent about $125 billion — as far as we can tell — in 2024, and the European allies spent about $500 billion, which is a lot.

So, I don’t see spending as the issue. How that money is spent is the real issue.

Which countries have nuclear weapons and might others decide to acquire some in light of the changing landscape?

The British have about 400 deployable warheads. These are essentially strategic warheads. They have three ballistic missile submarines.

The French have about the same number deployed in about the same way. Those can threaten the 10 largest Russian cities. Those are strategic weapons; they’re not intended to try to take out Russian missile silos.

The Russians have more than 10 times that many warheads. Are those deterrents effective for those countries? I think probably yes. Could they, or would they, extend their nuclear umbrella to neighbor states or to allies? I’m doubtful about that.

There’s been discussion in Germany about generating a nuclear capability, but it seems clear the Germans are not going to do that.

It wouldn’t surprise me if the Poles might be looking at that. The Ukrainians, who do have a lot of advanced technology and used to have nuclear weapons, it’s possible the Ukrainians might think about developing some kind of nuclear capability. Outside of those cases, I just don’t see it.

Are there any steps Europe can take immediately to defend itself?

No. 1: They can return to conscription because that enables you to grow your forces quickly and generate reserves.

No. 2: It’s really hard to move forces across Europe. This problem is called military mobility. Every time you cross a national boundary, or even a provincial boundary, you get stopped. There’s a paperwork check. The rail gauges are not uniform across Europe, so you might get as far as Poland and then you have to unload everything and put it on a different train. So military mobility is a real issue.

No. 3: Interoperability, which means can we all work together on the battlefield, is a real challenge.

All the Allies can’t talk on the battlefield securely to each other, and they can’t pass data securely on the battlefield because they have different systems.

And No. 4 is just be ready. You’ve got to be serious about the problem and attack it. I do think they’re getting more serious. The question is how fast can they do it, and is there going to be more Russian aggression on European territory before they get there?