Last July, James Mattis and Rex Tillerson arranged a tutoring session at the Pentagon for President Donald Trump in the secure, windowless meeting room known as "The Tank." The plan was to lay out why American troops are deployed in far-flung places across the globe, like Japan and South Korea. Mattis spoke first.

"The postwar, rules-based international order is the greatest gift of the greatest generation," Mattis told the president, according to two meeting attendees. The secretary of defense walked the president through the complex fabric of trade deals, military agreements and international alliances that make up the global system the victors established after World War II, touching off what one attendee described as a "food fight" and a "free for all" with the president and the rest of the group. Trump punctuated the session by loudly telling his secretaries of state and defense, at several points during the meeting, "I don't agree!" The meeting culminated with Tillerson, his now ousted secretary of state, fatefully complaining after the president left the room, that Trump was "a f[***]ing moron."