In his former life as a reality-television star, Donald J. Trump once declared, on air, “There is nothing worse than disloyalty.” In a Presidency marked by contradiction and chaos, this may be the closest he has come to giving us a unified theory of leadership. This week’s issue illuminates the approaches to power that may inspire President Trump—and the ones that may threaten him—as he seeks to shape domestic and foreign policy. Dexter Filkins profiles the Secretary of Defense, James Mattis, whose aggressive tactics may be Trumpian but whose thorough, scholarly appreciation of military history could not be less so. Joshua Yaffa looks at a multibillion-dollar bridge from Russia to Crimea being built by Vladimir Putin’s childhood friend—one of many who’ve made a fortune in inflated government contracts by cementing their ties to the Kremlin. Ryan Lizza sits down with the former acting Attorney General Sally Yates as she discusses, for the first time, how her resistance to Trump’s travel ban led to her dismissal. And in Comment, Evan Osnos unpacks the legacy of political resignations—which, in tandem with the high-profile firings of Yates, the former F.B.I. director James Comey, and others, may prove crucial in the months ahead. At home and abroad, we see those at the highest levels of public office giving unprecedented leeway to their inner circles—and taking radical measures to silence those who won’t pledge allegiance. President Trump, for his part, may find that there are worse things than disloyalty: an independent counsel, for one.