The Revolution in Military Affairs: Why it Took Place and What it Means - This paper reports an analysis of the Revolution in Military Affairs, a central topic of the strategic debate since the end of the Cold War. Three main points are discussed. The first one is the historical root of the Revolution. In particular, it is emphasized that the crisis of legitimacy of the US army after the Vietnam War has had a positive, triggering effect over the process of modernization. The second section is dedicated to the analysis of the central concepts and meanings associated with the Revolution: information warfare, global positioning systems, the "system of the systems" and so on. The third issue discussed is the future of the US grand strategy. Here the authors try to shed some light on the strategic dilemmas American decision makers shall deal with over the next few decades and conclude that the durability of the American primacy relies on four main factors: the state of the American economy, the timing of confrontation with its rivals, the spread of new technologies, and the development of the terrorist threat to American security.