This book explores the attitudes of the Spanish army officer corps towards the evolution of warfare during the early decades of the twentieth century, and their influence on the armies of the Spanish Civil War. It examines how the Spanish military coped with technological innovations such as the machine gun and the tank, how it adapted the army ́s battlefield doctrine to changes in warfare before the Civil War, and the influence of this doctrine on the outcome of the conflict. Of the different armed forces that fought in the Spanish Civil War, it is paradoxically the Spanish army that remains most forgotten - especially its military doctrine. Scholarship on the Spanish military in this period focuses on its politics, ideology and institutional reforms, touching upon 'hard' professional issues only superficially, if at all. Based on original research and using largely unstudied Spanish primary sources, this book fills a major scholarly gap in the history of the Spanish army and the Spanish Civil War.