Hundred Years' War (1415–53)
By 1449, the French had retaken Rouen. In 1450 the Count of Clermont and Arthur de Richemont, Earl of Richmond, of the Montfort family (the future Arthur III, Duke of Brittany) caught an English army attempting to relieve Caen at the Battle of Formigny and defeated it. The English army was attacked from the flank and rear by Richemont's force just as they were on the verge of beating Clermont's army. The French proceeded to capture Caen on July 6 and Bordeaux and Bayonne in 1451. The attempt by Talbot to retake Guyenne, though initially welcomed by the locals, was crushed by Jean Bureau and his cannons at the Battle of Castillon in 1453 where Talbot had led a small Anglo-Gascon force in a frontal attack on an entrenched camp. This is considered the last battle of the Hundred Years' War.
War of the Breton Succession
Up to this point, the succession crisis had been a purely internal affair. But to complicate things further, the Hundred Years' War between England and France had broken out four years earlier, in 1337. In 1341, there was truce between the two countries, but there was little doubt that hostilities would be renewed when the truce ended in June 1342. Thus, when rumours reached Philip VI of France that John of Montfort had received English agents, the French Crown naturally took a more direct interest in the situation. Charles of Blois became the official French candidate. Whatever had been his original intentions, John of Montfort was now forced to support Edward III of England as King of France.