This book examines the development of the modern idea of militarism from its inception in the 1860s until the outbreak of World War I. Often regarded as the archetypical militarist state, Imperial Germany in fact witnessed a major controversy over the issue, as the arms race and the military-industrial complex displaced more traditional concerns about authoritarian rule, and militarism gradually acquired its modern meaning. Older radical traditions and the impact of Marxism are reassessed as Nicholas Stargardt examines the political history of German Social Democracy, the principal anti-militarist protagonist.