Throughout the world today there are obvious trouble spots that have the potential to explode into serious conflicts at any time in the immediate or distant future. This study examines what history suggests about the future possibilities and characteristics of war and the place that thinking about conflict deserves in the formation of American strategy in coming decades. The author offers a historical perspective to show that armed conflict between organized political groups has been mankind’s constant companion and that America must remain prepared to use its military power to deal with an unstable, uncertain, and fractious world. Williamson Murray shows that while there are aspects of human conflict that will not change no matter what advances in technology or computing power may occur, the character of war appears to be changing at an increasingly rapid pace with scientific advances providing new and more complex weapons, means of production, communications, and sensors, and myriad other inventions, all capable of altering the character of the battle space in unexpected fashions. He explains why the past is crucial to understanding many of the possibilities that lie in wait, as well as for any examination of the course of American strategy and military performance in the future—and warns that the moral and human results of the failure of American politicians and military leaders to recognize the implications of the past are already apparent.