Book excerpt: The question of what causes war has concerned statesmen since the time of Thucydides. The Steps to War utilizes new data on militarized interstate disputes from 1816 to 2001 to identify the factors that increase the probability that a crisis will escalate to war. In this book, Paul Senese and John Vasquez test one of the major behavioral explanations of war--the steps to war--by identifying the various factors that put two states at risk for war. Focusing on the era of classic international politics from 1816 to 1945, the Cold War, and the post-Cold War period, they look at the roles of territorial disputes, alliances, rivalry, and arms races and show how the likelihood of war increases significantly as these risk factors are combined. Senese and Vasquez argue that war is more likely in the presence of these factors because they increase threat perception and put both sides into a security dilemma. The Steps to War calls into question certain prevailing realist beliefs, like peace through strength, demonstrating how threatening to use force and engaging in power politics is more likely to lead to war than to peace.