Hundred Years' War (1415–53)
The Lancastrian War was the third and final phase of the Anglo-French Hundred Years' War. It lasted from 1415, when King Henry V of England invaded Normandy, to 1453, when the English lost Bordeaux. It followed a long period of peace from the end of the Caroline War in 1389. The phase was named after the House of Lancaster, the ruling house of the Kingdom of England, to which Henry V belonged.
Hundred Years' War
Tensions between the French and English monarchies can be traced back to the 1066 Norman conquest of England, in which the English throne was seized by the Duke of Normandy, a vassal of the King of France. As a result, the crown of England was held by a succession of nobles who already owned lands in France, which put them among the most powerful subjects of the French King, as they could now draw upon the economic power of England to enforce their interests in the mainland. To the kings of France, this dangerously threatened their royal authority, and so they would constantly try to undermine English rule in France, while the English monarchs would struggle to protect and expand their lands. This clash of interests was the root cause of much of the conflict between the French and English monarchies throughout the medieval era.