The series of intermittent conflicts between France and England that took place during the 14th and 15th centuries wasn’t classified as the “Hundred Years’ War” until 1823. Traditionally, the war is said to have begun in 1337 when Philip VI attempted to reclaim Guyenne (part of the region of Aquitaine in southwestern France) from King Edward III—who responded by laying claim to the French throne—and to have lasted until 1453 when the French claimed victory over the disputed territory at the Battle of Castillon. By this calculation, the Hundred Years’ War actually lasted 116 years.
However, the origin of the periodic fighting could conceivably be traced nearly 300 hundred years earlier to 1066, when William the Conqueror, the duke of Normandy, subjugated England and was crowned king. Technically a vassal of the king of France (as the duke of Normandy), William’s simultaneous new role as king of England ushered in a complex web of dynastic marriages in which descendants of both the French and English kingdoms could arguably lay claim to the same territories. Over time, these overseas possessions resulted in inevitable clashes, and by 1337, Philip VI’s declaration that Edward III had forfeited his right to Guyenne was just the push Edward needed to renew his claim to the French throne as the nephew and closest male relative of King Charles IV, who had died in 1328.
From the French perspective, the conventional dates attributed to the Hundred Years’ War (1337-1453) marked the beginning and end of English hostilities on French soil. However, the English retained possession of the port city of Calais until 1558 and continued to assert a claim to the French throne until King George III finally relinquished the title in 1800.