Aquitaine and Scotland turn a dynastic dispute into war

Edward III held Aquitaine, one of France's richest duchies, while also possessing a claim through his mother to the French royal line. He initially supported Philip of Valois, but Philip's backing of Scotland threatened England while Edward was already fighting along several frontiers. Edward answered by supporting Philip's rivals, turning reciprocal political pressure into the opening struggle of the Hundred Years War. The conflict would last roughly 116 years, interrupted by treaties that rarely erased preparations for renewed war.