US security guarantee to NATO is effectively dead, warns former Norwegian defence chief

The US security guarantee to NATO is “for all practical purposes dead,” according to Sverre Diesen, a researcher at the Norwegian Defence Research Establishment (FFI) and former chief of defence, who argues Europe has failed to recognise the shift in time.

Speaking to Dagbladet, Diesen said uncertainty undermines the very concept of a guarantee. “You can’t be ‘a little pregnant,'” he stated, pointing to former President Donald Trump’s repeated criticism of NATO allies and the US-Israel conflict with Iran as turning points. “All doubt should now be set aside as long as the Trump administration holds power.”

While politicians acknowledge transatlantic tensions, they maintain that US commitments to NATO remain unchanged. Diesen disputes this approach: “They may have had to say that until now, but I strongly doubt it’s wise to continue. The real question is whether we’re prepared to face the consequences of admitting the truth—because that forces us to ask what we’ll do instead.”

He believes Europe could defend itself without the US but lacks the political will to achieve the necessary unity. “We’ll have to live with far greater uncertainty unless we can persuade the Americans to rediscover their strategic interest in European allies,” he said, noting that the US cannot counter both Russia and China alone. His hope rests on “more responsible” future US leaders restoring traditional alliances.

The stakes are highest for Norway, Sweden, and Finland, Diesen argued. “We’re more dependent on the US than the rest of Europe. Geographically isolated on Russia’s flank, we rely on a power capable of projecting large forces across the ocean—something only the Americans can do.” His proposed solution is a stronger, integrated Scandinavian defence cooperation to create “strategic synergy,” though he acknowledges even this would not eliminate the need for allies.

Diesen’s broader concern is what he calls the “decay of norms,” citing Trump’s US as a nascent “neo-fascist banana republic” abandoning its role as the guarantor of the post-war order. “When the Americans casually discard their hegemonic role, the world risks sliding into geopolitical anarchy,” he warned. His new book, Vestens skjebnetid (The West’s Fateful Hour), explores these shifts, questioning whether Europe can—or will—adapt.