Discussion surrounding a potential United States (U.S.) withdrawal from NATO has remained one of the defining debates since the beginning of Donald Trump’s second presidency. In recent months, particularly following the war involving the U.S. and Israel against Iran, tensions within the alliance have intensified, with President Trump openly criticising several European NATO allies and questioning their value to the alliance. As a result, the central question is no longer limited to whether Washington could formally leave NATO. Increasingly, attention should shift toward a more pressing issue: could Europe manage its security independently without substantial American support? What would be the strategic, military, and economic cost of such a shift, and would European states be capable of rebuilding or reorganising their defence capabilities quickly enough to confront emerging threats?
Importantly, despite the significant legal, political, and institutional constraints facing any U.S. president seeking to withdraw from NATO entirely, Washington could still adopt alternative approaches that stop short of formal withdrawal while substantially reducing its role within the alliance. Such measures could include lowering financial contributions, scaling back troop deployments across Europe, or withdrawing critical weapons systems and strategic capabilities currently provided by the U.S. In such a scenario, how vulnerable would Europe become, and how prepared would it be to fill the resulting gaps?