Preventative war has a long history in international politics, but until it became an instrumental part of the 'Bush Doctrine', it was mostly overlooked. We know that there have been preventative wars throughout history, but the motivations behind them have remained elusive. Because of the relatively little attention focused on preventative action, there are many crucial questions that remain unanswered. What exactly constitutes preventative action? What differentiates preventative action from pre-emptive action? Are there significant differences between preventative strikes and full-on preventative wars? What is the relationship of preventive action to traditional concepts of deterrence, compellence, and international law? Finally, and most important, why do states initiate preventative action? Ultimately, the best avenue for understanding decisions to initiate preventative action is through a close examination of the individual leader responsible for such decisions. The theory of preventative action presented in this book is based upon the beliefs, values, and perceptions of leaders. This book examines five cases: British action in the Suez Canal Crisis, 1956; Israel's strike on Iraq's nuclear reactor, 1981; American preventive war planning, 1946-1954; Indian preventative war planning, 1982-2002; and America's war against Iraq, 2003. In each instance, preventative action was seriously considered, and yet it only occurred in three of the five cases. In the end, each case provides further evidence that individual leadership matters, and nowhere more so than in decisions involving preventative war.