"AN ENGROSSING STUDY.” _TIMES LITERARY SUPPLEMENT_, BOOKS OF THE YEAR 2025 A critical study of five historical armies that offers solutions for how contemporary forces need to change to deal with modern threats. The most important task of any government remains the defence of its state and its citizens. Traditionally governments have used armed forces to do this. World events and comparative peace in Europe since 1989 have led most European governments to lose their focus on defence. However, recent events have proved that war is now as nasty, violent, destructive and prevalent as it has ever been, and governments need to fundamentally re-think their relationship with armies and soldiers. History gives us several examples of states who have reconstructed their armies successfully, both on the field of battle but also in terms of how they relate to the state which it is their duty to protect. This book is about five armies who have adapted successfully: the 4th-century Roman army of Constantine the Great; the 15th-century Ottoman army of Sultan Mehmet II; Cromwell's New Model Army of the English Civil War; the Prussian Army of the Napoleonic Wars; and the US Army of the Second World War. Former senior military officer and renowned military historian Barney White-Spunner draws lessons from their experience to establish long-standing principles that are as relevant today as they were in the 4th century. It is a book about armies, their loyalties, their organisation and their souls.