This book, first published in 1973, examines seven revolutionary armies ranging from Cromwell's New Model Army to the Red Army of Mao Zedong. In each case it examines the mobilisation and organisation of the army, and the need to balance political ideals and aspirations with military cohesion and discipline, and social stability. This book is an outstanding example of a study of the relationship between the military and society, and shows that no revolution can succeed without an organised army and that few such armies can tolerate for long the ideology that created them.