Mad Dog Mattis. The Warrior Monk. Married to the Marine Corps. It’s all hype that embarrasses Gen. James Mattis, the chief of U.S. Central Command, who is preparing to retire this spring after one of the most productive four-decade sprints in uniform of his generation. To Marines, Mattis is Chaos, his call sign and nom de guerre. According to interviews with more than a half-dozen officers who know him well, Mattis is an iconoclast and innovator who strove to outmaneuver the enemy on the battlefield, paralysis in Washington and the “yes, sir!” culture of the military. Others, particularly civilians, consider...