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THE HAGUE – NATO’s mutual defense clause, Article 5, faced fresh scrutiny this week as former U.S. President Donald Trump reignited controversy over the alliance’s foundational security principle. Speaking aboard Air Force One ahead of the NATO summit, Trump said there are “numerous definitions” of the clause — casting uncertainty over America’s commitment to its allies.
While Trump later stated, “We’re with them all the way,” his shifting tone left European leaders unsettled. It was a stark reminder of past moments when Trump questioned whether NATO members would reciprocate American support in times of crisis.
What Is Article 5?
Article 5 of the 1949 North Atlantic Treaty asserts that an attack on one NATO member is an attack on all. It was invoked only once — in solidarity with the U.S. after the September 11 attacks. However, the clause has long been strategically vague, allowing countries to determine what kind of response is “necessary.”
“When Trump says there are many interpretations of Article 5, he’s technically right,” said Olivier Kempf of the Foundation of Strategic Research. “It’s a leap of faith. It only works because members trust each other.”
Growing Tensions and Budget Demands
Trump has consistently accused NATO members — especially in Europe — of underpaying and freeloading off American military strength. At the summit, he went further, demanding an increase in defense spending to 5% of GDP by 2035, up from the current 2% target.
“NATO was broke,” Trump said. “Then I said, ‘You’re going to have to lift it to 4% or 5%, and 5% is better.’”
To secure U.S. endorsement of a joint declaration reaffirming Article 5, NATO members agreed to the new 5% goal. While seen by some as capitulation, others — including Finnish President Alexander Stubb — viewed it as a shift toward a more balanced, European-led NATO in the wake of Russian aggression.
A Shaky Reassurance
Despite Trump's final remark — “I stand with Article 5” — the moment highlighted how fragile NATO’s cornerstone remains. Trust, not treaties, is the glue holding the alliance together.
“The Europeans will sign anything, even if their insurance premium just doubled,” said Kempf, “because the world is more dangerous now.”
With elections looming and the world watching, NATO’s unity may depend less on declarations and more on whether U.S. leadership under Trump — or anyone else — truly honors the alliance’s most sacred vow.