This book provides an intellectual history of international relations theory from 1919 to the present, examining the dominance of realist theories, and their limited ability to explain world politics accurately. The volume presents the original text of John Vasquez's classic 1983 volume, The Power of Power Politics, analyzing classical realism and quantitative international politics, plus six new chapters covering the most important intellectual currents relevant to the debate on realism. This book is a major contribution to debates over realism in international relations, of interest to students as well as scholars.