President Donald J. Trump failed to achieve his often repeated preelection vow to end Russia's war against Ukraine "in 24 hours," but the 47th president still accomplished something extraordinary.
In less than three months, he called into question the security architecture that not only has deterred Russian aggression, but also kept Europe relatively peaceful and prosperous for over 75 years through 14 different administrations, including his own first term.
The U.S.-led North Atlantic Treaty Organization, an alliance of 31 European nations plus Canada, has been the backbone of Europe's defense since its creation in the ashes of World War II 80 years ago.
But Trump's hostility toward Ukrainian President Volodymyr Zelenskyy, his enigmatic embrace of Russia's Vladimir Putin, and his threats to abandon the alliance and refuse to defend America's NATO allies "if they don't pay" have prompted European leaders to think the previously unthinkable: Must Europe prepare to defend itself without American support? And given America's traditional leadership, is Europe capable of doing so?
Experts are divided over whether Europe could truly go it alone. John E. Herbst, a former U.S. ambassador to Ukraine who is currently a senior director at the Atlantic Council, argues that both Ukraine and Europe are capable of defending themselves — if they can marshal the political will.
But Alexander Vershbow, a former deputy secretary general of NATO, is skeptical.
Writing in Foreign Affairs magazine last May, before Trump's reelection, he and two coauthors warned that Trump was likely to downgrade, and perhaps even withdraw from the alliance, and that NATO itself would be unlikely to survive without American leadership and backing. Nothing he has seen since Trump's inauguration, he said in a recent interview, had changed his view.
For America's most trusted European allies, Trump's threats and chaotic, often contradictory policy pronouncements initially created shock — without the awe.
But his conciliatory posture toward Moscow, coupled with Russia's 2022 invasion of Ukraine, goaded Europeans — finally — to spend more on their own defense.
Soon after Trump's inauguration, U.K. Prime Minister Keir Starmer announced that Britain would raise military spending from 2.3% of gross national product to 2.5 % by 2027, the largest increase in military spending since the Cold War, three years faster than initially planned.
By 2030, he vowed, Britain would spend 3% of GDP, almost what Washington spends. Denmark, too, pledged to increase its military investments, with Danish Prime Minister Mette Frederiksen instructing her defense minister to "buy, buy, buy."
Putin's brutal invasion of Ukraine in 2022 was the initial catalyst for Europe's reversal of its longstanding military free riding.
Two years earlier, only nine NATO members were spending 2% of their GDP on defense. By last year, 21 members had hit the 2% target. Poland, which shares a historically contested border with Russia, has doubled its defense budget since Moscow's invasion of Ukraine and says it will spend 4.7% of its GDP on the military this year.
Germany, Europe's largest industrial power and largest economy, has agreed to create a 500 billion euro fund for infrastructure investment, and exempt from its debt brake all defense spending above 1% of GDP — with no upper limit.
"This would have been unthinkable just a few years ago," says Ian Bremmer, founder and president of the Eurasia Group, a political risk research and consulting firm. On paper, Europeans seem to have more than sufficient forces to deter or repel a Russian invasion.
"What we've seen of Mr. Putin's army is they are certainly not 10 feet tall," retired U.S. Air Force Gen. Philip Breedlove, a former NATO supreme allied commander, recently told The Wall Street Journal. "They have struggled mightily in fighting Ukraine."
According to the International Institute of Strategic Studies, NATO countries have more than a million troops and modern weaponry at their disposal — more than enough to replace the 80,000 U.S. troops who were stationed in Europe at the end of 2024.
Together, NATO members have some 5,000 tanks, versus the 3,000 tanks that Russia has after its battles in Ukraine.
The alliance has 2,800 self-propelled artillery systems, almost twice as many as Russia, and 2,000 jet fighters and other planes. Russia's air force, by contrast, has an estimated 1,000 fighters, bombers, and ground attack aircraft.
Even if the U.S. withdrew from the alliance, it would still leave critical infrastructure behind. European forces could occupy the 31 permanent bases that the U.S. now operates.
But as many defense analysts note, numbers do not tell the entire story. While Europe has twice the number of planes as Russia, for instance, its planes lack what Justin Bronk of the Royal United Services Institute (RUSI), a London-based think tank, calculates are enough munitions to destroy Russia's air defenses or hit distant targets on land or in the air.
Moreover, surveillance and intelligence information that enables those planes to find and assess targets "are almost exclusively provided by the U.S.," Bronk recently told The Economist.
Or, as Vershbow argued in his Foreign Affairs article last May, on its own, NATO would lack critical tools needed for a successful defense — "airlift capabilities, air-to-air refueling, high-altitude air defense, space assets, and operational intelligence" — all of which the U.S. now supplies. An even more daunting problem is command and control — or who would lead and coordinate operations in a war. An American general has led NATO's command structure — overseeing the military activities of all NATO members ever since its creation, Vershbow wrote.
"It is doubtful that any other country in the alliance could play this role." Britain and France have been discussing not only a joint European force to support Ukraine, but whether they could replicate America's nuclear shield, the cornerstone of the alliance, if Trump withdraws it. Together, Britain and France have around 400 nuclear warheads; Russia has 1,700.
And Britain's small nuclear deterrent already consumes a fifth of all its military spending, and Washington provides the missiles for its nuclear submarines.
An effort to double or triple the number of nuclear weapons would take years and divert funds for a simultaneous conventional buildup.
The most vexing challenge of all is leadership: Can Europe muster the political will to make such changes?
There are promising signs. In 2024, six European countries agreed to develop ground-launched cruise missiles and work together to increase their munitions production capacity and diversify their suppliers, seeking weapons from Brazil, Israel, and South Korea.
But Europe's military buildup would require buy-in at the national level among states long suspicious of each other.
Europe has no defense union yet, and skeptics say the European Union has proven unable to forge such unity and joint action.
The EU has so far been unwilling to fully integrate their nonmilitary economies. The largest commercial enterprises — banks, automakers, oil companies — remain strictly national enterprises.
There have been surprisingly few cross-border mergers despite the existence of a European Parliament, a European central bank, a common currency that includes most European members, open borders, and a hugely expensive army of European bureaucrats.
"Our industry is still too small . . . too fragmented, and to be honest, it is too slow," NATO Secretary General Mark Rutte told the European Parliament last year.
While Europeans are scrambling to boost their military production, Vershbow estimates that Europe would need about a decade to produce what it needs for a military confrontation, while Russia could do so in about two or three years.
Yet even in Brussels there are signs of change.
Since Trump's inauguration, the EU has created a 150 billion euro supranational loan facility for military purchases, and loosened rules that prevent the European Investment Bank from investing in the defense sector.
A rare successful example of cross-border industrial integration in defense is MBDA, a missile manufacturer jointly owned by Britain, France, and Italy.
In effect, Trump, says Zanny Minton Beddoes, The Economist's chief editor, is forcing Europe to become more "Trumpian."
Bremmer says that European defense integration is likely to be affected by factors beyond its control, such as the nature of the U.S.-Russia relationship.
If they become partners, the security challenges Europeans face will only grow.
Similarly, if populist, right-wing parties such as the Alternative for Germany come to power, "it's hard to see the EU holding together as a strong, independent, and integrated defense and economic actor," he said.
Finally, Trump's own political fortunes matter. While Trump accomplished an extraordinary amount during his initial months in office, Bremmer wonders whether he can sustain such momentum for an entire term. Judith Miller is a Pulitzer Prize-winning investigative reporter and an expert on U.S. foreign policy.