Charles I or Charlemagne united most of Western Europe during the Middle Ages and laid the foundations for modern France and Germany. He was the first recognized Roman emperor in the West since the collapse of the Roman Empire three centuries earlier and ruled absolutely over a vast domain for thirteen years.
Einhard’s biography of the Carolingian Empire’s founder 'The Life of Charlemagne: Vita Karoli Magni' is one of the most famous pieces of literature on the early Middle Ages. It is both an epic and personal account of the legendary warrior king who was known as the Father of Europe, providing fascinating insight into his political success, battlefield strategy, foreign and domestic policies, friends, enemies and personal habits. For scholars of military science it is an essential bridge text linking the masterworks of ancient strategy like 'The Art of War' and 'Commentarii de Bello Gallico' with the future writings of Machiavelli, Clausewitz, et al.
