The debate about the conflict which transformed Europe between 1914 and 1918 is one of the most fundamental in modern European history. This book, based on public lectures given in Oxford, makes two distinctive contributions to that debate. It presents readable and judicious accounts of the events and decisions which directly precipitated the outbreak of war in each of the main countries and assesses the role of public opinion and popular mood in determining and responding to the "July Crisis." The book offers a stimulating survey of the historiography of the immediate causes of the war, before and since the famous "Fischer controversy" over German responsibility, and new reflections on the character of the official and unofficial "mentalites" during the last weeks of peace. Published on the seventieth anniversary of the 1918 Armistice, this book will appeal to anyone interested in how wars begin.