Excerpts from Books and Wikipedia
"The Battle of Bouvines, which took place on 27 July 1214, was a medieval battle which ended the 1202–1214 Anglo-French War. It was fundamental in the early development of France in the Middle Ages by confirming the French crown's sovereignty over the Angevin lands of Brittany and Normandy.
Philip Augustus of France defeated an army consisting of Imperial German, English and Flemish soldiers, led by Otto IV, Holy Roman Emperor in the north. Allied with Philip was Frederick II Hohenstaufen, who controlled the southern Holy Roman Empire and afterwards deposed Otto. . . . Philip was himself able to take undisputed control of most of the territories in France that had belonged to King John of England, Otto's maternal uncle and ally." [Wikipedia] "Phillip's victory virtually created the nation of France, whereas Otto's defeat led to a weakening of the Holy Roman Empire and Germany's long-lasting dissension. English King John's inability to muster support for the campaign led to his weakening via the Magna Carta."