As a presidential candidate, Donald Trump broke not only from the Republican Party but also from the bipartisan consensus on the direction of recent U.S. foreign policy. Calling the Iraq war a terrible mistake and lamenting America's nation building expeditions, Trump evinced little interest in maintaining the traditional form of American leadership of the liberal international order. He threatened to pull the United States out of NATO, complained that the United States was being taken advantage of by its trading partners, and argued that immigration was a terrible threat. Instead, Trump's “America First” vision called for a reassertion of American nationalism on the economic front as well as in foreign affairs. Since Trump took office, it has become clear that “America First” was more campaign slogan than coherent vision of American grand strategy and foreign policy. As president Trump has steered a course that has maintained some of the worst aspects of previous foreign policy – namely the pursuit of primacy and frequent military intervention – while managing to make a new set of mistakes all his own. This book provides an assessment of Trump's America First doctrine, its performance to date, and its implications for the future.