NATO leaders gather in Ankara to address U.S.-European tensions, defense gaps, and support for Ukraine’s military resilience.
The aftermath of the Ukraine war and the Iran conflict are high on the agenda at this week’s NATO summit. But long before Secretary-General Mark Rutte took to the stage on Tuesday, NATO’s most powerful figure was already setting the tone.
“It is foolish for the United States to continue down this unilateral path when the relationship is not mutually beneficial,” President Donald Trump wrote late last week. “They weren’t there for us!!!”
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As the transatlantic organization’s 32 leaders gather in Ankara for a two-day summit starting Tuesday, chilly relations between military alliance members and the United States have emerged as the biggest challenge to the military alliance’s future.
NATO says the summit will focus on three priorities: increasing defense investment, expanding Europe’s defense industrial base and securing long-term military support for Ukraine. The meeting comes after the allies pledged last year to spend the equivalent of 5% of their gross domestic product (GDP) on defense, with European allies and Canada set to increase defense spending by a nominal $139 billion in 2025 alone.
But talks will be overshadowed by President Trump’s threat to withdraw the United States from the North Atlantic Treaty Organization (NATO) and plans to transfer troops and weapons from Europe. On May 1, the Pentagon announced it would withdraw approximately 5,000 troops from Germany following a “thorough review of the Department’s military posture in Europe.”
“I don’t think the alliance has reached a breaking point,” said Ian Lesser, a distinguished fellow at the German Marshall Fund. “But we are entering a period of serious adjustment.”
President Trump’s skepticism about NATO is nothing new, but the recent standoff with Iran has deepened tensions within the alliance. He has repeatedly criticized European allies for refusing to assist the United States militarily, particularly by refusing to join efforts to reopen the Strait of Hormuz.
Another major source of friction is military spending. On Thursday, President Trump again criticized the defense alliance, saying it was “ridiculous” that the United States spends more money on NATO than any other country “without getting any benefit” to protect it.
Experts say that while the United States is changing its attitude toward NATO, it is unlikely to leave the organization given the legal and political challenges at hand, especially as the United States prepares for crucial midterm elections that will determine whether it retains control of Congress.
To formally withdraw, President Trump would need a two-thirds majority in the U.S. Senate or a vote from Congress, but NATO still enjoys broad support among many members of both major political parties in Washington, making this scenario unlikely to materialize anytime soon. “It is in the United States’ interest to remain engaged in European security and to maintain an important role in NATO, and this is a view shared on both sides of the aisle in Washington,” Lesser said.
Sophia Besch, a senior fellow in the European program at the Carnegie Endowment for International Peace, said she hoped the summit would be an opportunity to make some plans, even though European countries have given up on restoring the trust built on decades of alliances.
“What they still want is more predictability. They accept that the U.S. commitment to Europe is changing. What they want is a more orderly version of the transition,” Besch said. “The concerns behind this are well-founded. A failed handover from a US-led NATO to a European-led NATO will leave a hole in our deterrence and defense capabilities.”
Despite concerns about a potential decline in U.S. support, European allies will not be left defenseless. Russia’s invasion of Ukraine exposed the fragility of Europe’s defense industrial base and the extent to which many NATO members depend on the United States for critical military capabilities. At the same time, repeated tensions in transatlantic relations, from conflicts within NATO to President Trump’s threat to seize Greenland, are fueling calls for greater European strategic autonomy. As a result, European allies’ defense spending increased by 62% between 2020 and 2025.
However, significant capability gaps remain. According to the International Institute for Security Studies (IISS), European countries continue to rely heavily on the United States for long-range strike capabilities, intelligence, surveillance and reconnaissance, satellite-based assets, logistics, and integrated air and missile defense.
Bridging these gaps will be a long-term challenge. The IISS estimates that replacing America’s most important conventional forces would cost about $1 trillion and could take more than a decade. Europe’s defense industry also faces difficulties in scaling up production fast enough, while many militaries continue to struggle with recruitment and retention.
