Newly available primary source material challenges many of the long-held assumptions about the origins of World War I. This article discusses the latest historical scholarship most relevant to international relations theory and the field of international security. The main conclusion is that much of the new evidence runs counter to security dilemma theory and key tenets of defensive realism. Common depictions of World War I being triggered by a “cult of the offensive,” a “short-war illusion,” spiral dynamics, or preemptive strike incentives do not accord with the empirical record. Instead, the evidence suggests that German leaders went to war in 1914 with eyes wide open. They provoked a war to achieve their goal of dominating the European continent, and did so aware that the coming conflict would almost certainly be long and bloody. They neither misjudged the nature of modern military technology nor attacked out of fear of Germany’s enemies moving first. In light of the new historiography, international relations scholars should reexamine their empirical understandings of this conflict, as well as their theoretical presuppositions about the causes of war. Keir A. Lieber, The New History of World War I and What It Means for International Relations Theory. Source: International Security, Vol. 32, No. 2 (Fall, 2007), pp. 155-191