President Trump has never had much love for the NATO alliance, which he thinks is overdependent on American largess, and in his first term, talked about abandoning the collective defense pact.
In his second term, Mr. Trump and his senior officials have made it clear that the security of Europe is no longer the first priority of the United States, which wants to concentrate resources on its own border and the Indo-Pacific, where China has become a peer rival.
On Thursday, Mr. Trump suggested that the United States might not protect NATO members that he believed were not paying enough for their own defense, calling it “common sense.”
But what would Europeans need to do to replace the enormous American contribution to NATO?
The answer comes down to money, personnel, time and cooperation with Washington, said Ivo Daalder, a former American ambassador to NATO and a coauthor of a recent report from Harvard’s Belfer Center on how to create “a strong European pillar” in the alliance.
The central problem is that NATO was built as an American-dominated alliance, intentionally dependent on American leadership, sophisticated weaponry, intelligence and airlift. The current NATO command structure is essentially owned and operated by the United States, led by Gen. Christopher G. Cavoli.
“The United States is the linchpin of the alliance so we could control our allies and get them to do what we want,” Mr. Daalder said. More practically, the United States military is the skeleton of NATO, and “if you suddenly pull out the skeleton, the body dies.”
Money
Relative to other challenges, money is the easiest part of the European quandary. The question, as ever, is political will and commitment to spending larger sums — and the trade-offs and political costs it will entail.
Prime Minister Donald Tusk of Poland put it simply last week, saying: “500 million Europeans ask 300 million Americans to protect them from 140 million Russians.” What Europe lacks, he said, is “the belief that we are truly a global force.”
Friedrich Merz, who is on course to be the next chancellor of Germany, offered a bold response this week to the new pressures on Europe, proposing to spend nearly 1 trillion euros, or $1.07 trillion, on the military and infrastructure over the next 10 years.
Britain, Belgium, Poland and Denmark have also recently said they would spend more. On Thursday, E.U. leaders agreed to boost military spending outside normal debt limits. But overall, European nations remain far shy of the spending that experts say they will need to replace the American commitment.
Those estimates vary, but could mean a hike of €250 billion a year, or about 1.5 percent of the European Union’s gross domestic product, according to a study from two research institutions, Bruegel and the Kiel Institute for the World Economy.
The study recommends that European nations spend at least 3.5 percent of G.D.P. per year on the military; currently just five of 32 NATO members, including the United States, spend above 3 percent.
The Europeans possess a lot, but also need a lot more sophisticated weaponry, now largely provided by the United States. The biggest gaps are in integrated air and missile defense and long-range precision strike capability, said Ben Hodges, a former commander of the U.S. Army in Europe.
Europe also lacks “strategic enablers,” including transport aircraft, sophisticated drones and satellites — crucial systems for intelligence, surveillance and reconnaissance.
It has the capacity to produce more of its own weapons, he said. But that would require better coordination among nations to invest in the right industries and purchase jointly.
Ideally, Europe should have sufficient stocks of ammunition and missiles to fight a high-intensity war for at least six months, but those are badly depleted from the war in Ukraine.
A study by the International Institute for Strategic Studies found that even fundamentals like the number of combat battalions and in-service battle tanks have remained static or fallen since 2014, despite Russia’s annexation of Crimea.
Political will matters here, too — to overcome bureaucratic constraints and requirements on manufacturers.
The European Investment Bank is prohibited from providing loans to make weapons, though the European Union is rethinking the rule.
And German law requires that weapons makers have direct orders from the government before production can even start. That makes production for potential future sales impossible even if they have excess capacity now.
Personnel
Right now, there are only about 100,000 U.S. troops in Europe — a number that could fit into the University of Michigan’s football stadium — said Mr. Hodges, who used to command them.
Yet it seems almost impossible that the Europeans, even if they increase military spending, could quickly replace the bulk of them, let alone fight on their own for any extended period.
Of the U.S. troops, 20,000 were sent to Europe after Russia invaded Ukraine three years ago, to shore up NATO deterrence. Analysts expect the Trump administration to pull out those troops before too long.
Another 40,000 of the U.S. troops, Mr. Hodges said, are in Europe on expensive rotations, which Mr. Trump is also likely to want to stop.
There are multiple problems for Europe in replacing such numbers.
Only a handful of European nations still have conscription forces. And attracting the right recruits is hard; pay scales and career prospects are better in the civilian world. Even once soldiers are trained, especially in high-tech warfare or “back office” jobs like engineering or mechanics, it is hard to retain them.
Recent suggestions that Europeans put troops into Ukraine to secure a potential peace deal would put extra strain on personnel, potentially for the long term.
NATO is already pressing members to meet requirements for a new force model. Under that agreement, more than 300,000 troops would need to be available within 30 days to reinforce the alliance’s eastern flank against Russia in the event of a crisis.
For now, there are simply not enough soldiers, logistics specialists and intelligence officers to go around.
“European armies are too small to handle even the arms that they’ve got now,” said Jim Townsend, a former U.S. deputy assistant secretary of defense who is now at the Center for a New American Security.
“The British and the Danes, to pick two examples, are good militaries, but they would not be able to sustain intense combat for more than a couple of weeks,” he said. “It doesn’t matter how good you are if there aren’t enough of you.”
Time
The scale of what the Americans now handle for NATO is too big to replace quickly. To buy or produce the necessary equipment and recruit and train the necessary troops will simply take time.
In normal times, it would take a decade for Europe to catch up, said Camille Grand, a former NATO assistant secretary general, who wrote a detailed report about the problem for the European Council on Foreign Relations last year.
Today’s accelerated sense of urgency might help the Europeans do it a little sooner. But critics argue that Europe has waited far too long to respond to clear signaling from Mr. Trump’s first presidency, let alone to his Russia-friendly comments during the campaign.
American officials from both parties have been urging European allies to do more for their own defense for 50 years, and President Emmanuel Macron of France’s warnings in 2019 about fading American commitment to NATO were heard but largely unheeded.
The Europeans are finally trying to address the money problem. But they cannot magically reduce the time needed to make a transition from American domination of NATO in a way that would not damage their security sufficiently to tempt Russia to test the alliance.
Most importantly, it would require that the United States aid the transition and synchronize its withdrawals with the European buildup.
Cooperation
To move from a U.S.-dominated conventional defense of Europe to a European one could be very dangerous without American cooperation.
A sudden American withdrawal would be tremendously tempting for President Vladimir V. Putin of Russia, who wants to undermine NATO. The United States must be willing to wait to withdraw key capabilities until Europeans are ready to take them over, Mr. Daalder said.
Even in Ukraine, with its 900,000 soldiers helping to pin down the Russian army, a European commitment of even 30,000 to 40,000 peacekeeping troops could undercut NATO’s ability to deter Russia from testing the alliance in the Baltics, for example.
That has led some experts to suggest that a European force in Ukraine should be a NATO force, without U.S. troops on the ground, something Mr. Trump has in any case ruled out. But a NATO force, at least, could use existing NATO assets, like surveillance planes and intelligence capabilities, within the NATO command structure.
Others, like Max Bergmann of the Center for Strategic and International Studies, think it’s time to revisit the concept of a European army, which had long been opposed by the United States.
A unified army, he suggests, would go a long way to ending duplication and making spending more efficient. But who would command such an army, and under what political authority, are difficult questions to answer.
A standing European army, he argues, need not replace the United States in each capacity but could be integrated into NATO and be robust enough to do its main job: to deter Russia from invading member states.
After all, he notes, “Europe on paper has nearly 2 million personnel in uniform and spends roughly $338 billion per year on defense, more than enough to deter Russia and enough to make Europe collectively a military power.”
