This gem of a book is the story of the battle between pacifism and militarism in Europe over the past century -- and the story of how pacifism won. At the start of the twentieth century, pacifism and militarism "existed side by side" in Europe. Influential writers, such as Ivan Bloch and Norman Angell, argued that modern technology had made warfare so potentially violent that it could not possibly make sense any longer, while their critics, such as the German military historian Hans Delbrück and the American strategist Alfred Thayer Mahan, insisted that war could still be necessary, just, and even glorious. The unprecedented destruction of two world wars catastrophically illustrated Bloch's and Angell's point -- the first leaving a majority of Europeans determined "never again" to wage war, the second driving that message home to the entire continent. Postwar Europeans, after two generations of fratricide, focused on building "civilian states," a posture made possible by the U.S. nuclear umbrella. Still today, Sheehan reports, despite the end of the Cold War and fitful efforts to develop the European Union's defense capabilities, European military budgets continue to fall and Europe's citizens reject military force as a tool of national policy. The sources of Europe's antimilitarism have been examined by other scholars, but Sheehan's vivid historical narrative adds value by giving the reader a real feeling for how their experience with warfare as an allegedly rational policy tool led Europeans to abandon it. This book is a model for how good history can be used to explain the present.