The war grew into a broader military, economic, and political struggle involving factions from across Western Europe , fuelled by emerging nationalism on both sides. The periodisation of the war typically charts it as taking place over years. However, it was an intermittent conflict which was frequently interrupted by external factors, such as the Black Death , and several years of truces. During the war, five generations of kings from two rival dynasties fought for the throne of France, which was then the wealthiest and most populous kingdom in Western Europe.
The war had a lasting effect on European history: both sides produced innovations in military technology and tactics, including professional standing armies and artillery, that permanently changed European warfare.
Chivalry , which reached its height during the conflict, subsequently declined. Stronger national identities took root in both kingdoms, which became more centralized and gradually emerged as global powers. The term "Hundred Years' War" was adopted by later historians as a historiographical periodisation to encompass dynastically related conflicts, constructing the longest military conflict in European history. Each side drew many allies into the conflict, with English forces initially prevailing; however, the French forces under the House of Valois ultimately retained control over the Kingdom of France.
The French and English monarchies thereafter remained separate, despite the monarchs of England later Britain styling themselves as sovereigns of France until The root causes of the conflict can be traced to the crisis of 14th-century Europe. The outbreak of war was motivated by a gradual rise in tension between the kings of France and England over territory; the official pretext was the interruption of the direct male line of the Capetian dynasty.
Tensions between the French and English crowns had gone back centuries to the origins of the English royal family, which was French Norman , and later, Angevin in origin through William the Conqueror , the Norman duke who became King of England in English monarchs had, therefore, historically held titles and lands within France , which made them vassals to the kings of France. The status of the English king's French fiefs was a significant source of conflict between the two monarchies throughout the Middle Ages.
