Answer:
By engaging in warfare against the pagan Saxons for over three decades, forcing them to convert to Christianity, and unifying Europe.
Explanation:
Charlemagne, who was also known as Charles the Great ruled a major portion of Western Europe in medieval times.
He went about seeking to bring all the people together and unite them and he accomplished this by fighting and winning several wars against the Saxons and trying to unite Bavaria, the Lombards, and the Avars.
His efforts were recognized in 800 when the Pope crowned him the "Emperor of the Romans".
His empire would go on to last generations because of his ruthlessness and fight for Christianity in Western Europe.
