Why Mattis Had to Go

James Mattis is not an imposing man. At 5-foot-9, with a slight build, he doesn’t have the physical presence you might expect from someone whose nickname is “Mad Dog.” He doesn’t have, say, H.R. McMaster’s bull neck or booming voice. Yet Mattis loomed large over U.S. national security policy, such as it is, under this presidency—so much so that his long-expected but still-sudden resignation Thursday had Washington reporters competing to see who could dial up the most hair-raising quotes warning of catastrophe ahead.