The major conflict that involved multiple nations in Europe from 1337 to 1453 was the Hundred Years' War. This prolonged struggle primarily pitted the Kingdom of England against the Kingdom of France, frequently involving various allies and mercenaries. The war was characterized by several notable battles, including Crécy and Agincourt, and it significantly transformed military tactics and national identities. The conflict arose from territorial disputes and claims to the French throne, ultimately leading to a sense of nationalism in both England and France. The end of the war saw increased centralization in France and the decline of English territorial ambitions in mainland Europe.