While modern-day allies, France and England had quite a notable string of wars against each other since the days of the monarchies. However there was no wars between France and England until after the reign of William the Conqueror. William was Duke of Normandy which gave him quite a considerable amount of de facto power in France. Through French princesses being ancestors, Kings of England had a strong claim to the French throne (the main being through King Edward III) when direct-male lines to the French throne died out. Their claims to their lands (or throne) in France were the main causes for such wars.