One of the more unusual topics of this very unusual election year has been the hitherto uncontroversial issue of the U.S. commitment to NATO. Last month, in his characteristically blunt fashion, Republican presidential candidate Donald Trump slammed NATO for being “obsolete.” This week, as he swept closer to the GOP nomination, he softened that to “outdated” but repeated his call for changes — including making allies pay more. Democratic candidate Bernie Sanders similarly has argued that the United States should scale back its NATO commitments.

These ideas have drawn ferocious criticism from the defense and foreign policy establishments, including the Pentagon and former secretary of State Hillary Clinton. Victor Davis Hanson, a historian at the Hoover Institute, acknowledged the salience of Trump’s argument but then backflipped to argue for the organization’s continued relevance anyway: “A powerful Russia will always have to be watched. A dynamic and headstrong Germany will always have to be integrated into some sort of military alliance. And the United States will always have a natural self-interest in pre-emptively keeping kindred Europeans from killing each other.”