IN FUNDAMENTAL WAYS I have been writing this book since I began to study the history of U.S. foreign relations as an undergraduate at Cornell University in the late 1960s. There, in an environment defined by the Vietnam War, I along with hundreds of my fellow students gathered in Bailey Hall on Tuesday, Thursday, and Saturday mornings to listen spellbound to lectures by Walter LaFeber. It was during this time that I started to think about an American empire, and more precisely, the relationship between that empire and America's “mission” of expanding the sphere of liberty. For this I owe my first thanks to Walt; to those to whom he introduced me either directly or indirectly, William Appleman Williams, Lloyd Gardner, Tom McCormick, and their colleagues; and to my peers at Cornell who were so responsible for encouraging me to think differently than I had thought before.
Over the subsequent decades, as I developed my own courses, taught my own students, and wrote my own books, the seeds of this book continued to germinate. I won't even try to acknowledge all of those who contributed to its growth. They know who they are. But I must single out two. No one has influenced how I think and write about history as much as a political scientist—Fired Greenstein. Not only did Fired reassure me that, notwithstanding the historiographic trajectory that accompanied that of my career, individuals do matter, but he also instructed and inspired me in ways that transformed my disposition to write about people into a scholarly undertaking. The second person I must thank specifically is at the other end of my professional spectrum: Jeffrey Engel. I did not know Jeff until he came to Temple some half–dozen years ago as a visiting fellow at the Center for the Study of Force and Diplomacy (recommended, as is only appropriate, by Walt LaFeber and Tom McCormick). But since then, particularly as I struggled with a variety of administrative responsibilities and other “diversions,” Jeff's energy, commitment, and relentless good cheer helped me keep my eye on the ball. Indeed, he