What is "grand strategy," and why is it seemingly so important and so difficult? This monograph explores the concept of grand strategy as it has developed over the past several decades. It explains why the concept is so ubiquitous in discussions of present-day foreign policy, examines why American officials often find the formulation of a successful grand strategy to be such an exacting task, and explores the ways in which having a grand strategy can be both useful and problematic. It illustrates these points via an analysis of two key periods in modern American grand strategy -- the Truman years at the outset of the Cold War, and the Nixon-Kissinger years in the late 1960s and 1970s -- and provides several suggestions for how U.S. officials might approach the challenges of grand strategy in the 21st century.