The Alliance began with a manageable core group of twelve nations. But through nine separate rounds of expansion, it now includes previous Warsaw Pact members, which sought protection from their former occupier by moving under the Alliance’s nuclear umbrella. It has also welcomed former neutral and nonaligned states that see Russia’s current revanchism as an existential threat to their independence. These additional members have brought the Alliance to a membership of thirty-two states.
Under the terms of NATO’s founding document, the 1949 Washington Treaty, admission of new members to the Alliance is based on the unanimous consent of the existing members. This consensus principle has over time evolved into a norm governing how NATO makes decisions. The fact is, however, that the principle, except in the case of accession, is not enshrined or codified in any Alliance document. What worked for the Alliance earlier, when all of its members were like-minded states facing an overwhelming military challenge and the memories of World War II were fresh in the minds of both publics and leaders, may not be fit for purpose today with a broader and much more diverse membership.
Given the threatening international backdrop and the need to balance the cohesion of a larger Alliance with the ability to make rapid and resolute decisions, has the time come to revise the consensus model in critical Article 5 situations?