Secretary of Defense Jim Mattis has given everything to America: 44 years in the Marine Corps and 2 years of service at the Pentagon. But if he is open to a new challenge and responsibility, he should become the next NATO secretary general.

A longtime supporter of the alliance and of its need for European member states and Canada to spend more on defense and more of their defense budgets on equipment, Mattis would be a natural fit. Indeed, Mattis would be the most natural fit of anyone on Earth. First, he retains specific military experience with NATO from his time as the commanding general of NATO’s Transformation Command. Second, Mattis is keenly astute to NATO’s mission, capabilities, and vulnerabilities from his time as Defense secretary.