After King Edward II had married Princess Isabella of France, their son, King Edward III, was now a legitimate heir to the French throne, and eventually the dynastic dispute resulting from this caused tensions between England and France. Tensions eventually boiled over when Britain invaded France in 1337 at Normandy and the King of France asked his ally, John VI of Constantinople, for help. John VI built a system of allies against England, which included Castille, Scotland, Genoa, Venice, and Florence, lead by John VI to France, with an army massing up to 300,000 soldiers, of which there 120,000 Infantrymen, 80,000 Knights, 50,000 Archers and Crossbowmen, and the remaining 50,000 were support soldiers, and along with the Byzantines came 200 cannons.