The Hundred Years' War was a series of conflicts that engulfed Europe between 1337 and 1453. Although the main opponents were England and France, other powers were often pulled into the conflicts. The main issue at stake had to do with a relationship between England and France dating back to the Norman conquest. Because of this history, England had territories in France and France claimed the monarch of England as a vassal. The end of the war settled many territorial claims.
Henry V's victory at the Battle of Agincourt in 1424 resulted in England gaining the upper hand in the war. Simultaneously, the heir to the French throne, the Dauphin (who was crowned as Charles VII), was in a politically precarious position, with the succession being called into doubt, with Henry VI of England having an equally strong claim to the French throne as the Dauphin.
Into this tumultuous situation, Joan of Arc claimed that religious visions sent her to support the Dauphin and led the French armies to several victories, beginning with freeing the besieged city of Orléans in 1429. Although she did not actually wield weapons or directly control tactics, her presence inspired the French to a series of victories and her enthusiasm for bold aggressive strategies changed the course of the war, switching the momentum to the French cause.