This book examines a number of major blockades, including the Continental System in the NapoleonicWars, theWar of 1812, the American CivilWar, and World Wars I and II, in addition to the increased use of peacetime blockades and sanctions with the hope of avoidingwar. The impact of newtechnology and organizational changes on the nature of blockades and their effectiveness as military measures are discussed. Legal, economic, and political questions are explored to understand the various constraints on belligerent behavior. The analyses draw on the extensive amount of quantitative material available from military publications.