From the first days of his reign, Charlemagne was harassed by the Saxons, a tribal people who practiced a primitive form of earth worship. In 722, before his Italian campaign, he had made his first march against them, taking Paderborn and the fort of Eresburg.
At Paderborn, Charlemagne committed an act which was to color all of his pagan wars. In the name of Christianity, he desecrated a Saxon shrine, cutting down a sacred tree. Unlike the Romans in pre-Christian times, or the Moslems of his own day, Charlemagne was not content to allow alien religions to exist within the realm of his conquests. He inaugurated a brand of militant Christianity which was to have profound repercussions in Europe and the Near East during the later Middle Ages.
While Charlemagne was in Italy fighting against the Lombards, the Saxons rose again. In 775, he repeated his earlier chastisement, destroying a stronghold at Silburg, dispersing the Angrarians, and crossing the Weser into Ostphalia, where he burned and sacked everything in sight. The leaders of Ostphalia and Angraria surrendered, accepted baptism and paid homage to Charlemagne. The king took Saxon youths as hostages and sent them to receive Christian educations in Austrasian monasteries.
In 777 a large assembly of Franks and Saxons met at Paderborn to demonstrate the conversion of the defeated Saxons. A large number of Frankish noblemen and churchmen attended. The Saxons received baptism and accepted Christian instruction in exchange for the right to retain control of their ancestral lands. At the same time, they swore absolute fidelity to their new sovereign.