Hundred years war

 ... was an intermittent struggle between England and France in the 14th–15th century over a series of disputes over territories & the question of the legitimate succession to the French crown:

• As the English kings started as Dukes of Normandy, their continental territories were a constant source of conflict.
• When the last Capet dynasty died without an heir, the English king Edward III claimed to have the rightful ruler of France over the newly Valois king, Philip the VI.

Initially, the English won quite a few battles but failed to unite England and France under one crown.

• 1346: The first battle of the war between Edward III of England & Philip VI of France took place at Crécy. The French lost.
• 1355: Edward the Black Prince, eldest son of Edward III, defeated the French once again at Poitiers, taking king John II of France prisoner. France agrees to pay the English & give them territories if Edward renounced his claim. Treaties were never respected. 
• 1415: Henry V of England destroys the French at Agincourt. The French were ruled by a mad king and the country was in a civil war between the Armagnacs, and the Burgundians. 
• 1428: The French push back when Joan of Arc relieved the siege of Orléans. She was captured by the Burgundians & died as a heretic. 
• 1475: Official end of the war. No peace treaty was ever signed. Calais was retained by the English until 1553, and English kings continued to claim the title king of France until 1801.