This book is a product of the extraordinary institutions whose support allowed us to write it; namely, the Johns Hopkins School of Advanced International Studies, Tufts University, and the American Enterprise Institute, where we first hatched the idea for the project in one of the Foreign and Defense Policy team’s regular seminars. It is also a product of exchanges with numerous individuals who helped shape our views, even if they might violently disagree with those views. An incomplete list would include James Baker, Sasha Baker, Jude Blanchette, Jason Blessing, Dan Blumenthal, Tarun Chhabra, Zack Cooper, Mackenzie Eaglen, Nicholas Eberstadt, Charles Edel, Francis Gavin, Michael Green, Adri Guha, Toby Harshaw, Jonathan Hillman, Robert Kagan, Colin Kahl, Klon Kitchen, Rebecca Lissner, Oriana Skylar Mastro, Andrew May, Evan Montgomery, Danielle Pletka, Mira Rapp-Hooper, Ely Ratner, Mary Sarotte, Kori Schake, Andrew Shearer, Derek Scissors, David Shipley, James Stavridis, James Steinberg, Jake Sullivan, and Thomas Wright. Dan Kurtz-Phelan at Foreign Affairs, Cameron Abadi at Foreign Policy, and Prashant Rao at The Atlantic published articles in which we began developing some of the ideas featured in this book. At Norton, John Glusman and Helen Thomaides were a delight to work with, as was our agent, Rafe Sagalyn. John Bolton (not that John Bolton), Zach Wheeler, and Emily Carr provided valuable research assistance. Our greatest thanks go, of course, to our families, who continued—during this as during previous projects—to show us far more strategic patience than we deserve.