The Hundred Years War was really a series of conflicts that took place between England and France between 1337 and 1453.
The key background piece of information is that in 1066 CE, the Duke of Normandy (France) crossed the English channel and killed King Harold at the Battle of Hastings.
Since that moment, England and France's royal families were constantly interconnected and both had designs on ruling BOTH England & France.
The War began with Edward III of England declaring himself to be King of France as well through his control of the Duchy of Aquitaine.
The War ended over 100 years later with the British King renouncing his claim to the French throne and a popular revolt in England starting the War of the Roses.
