Saxony contained four areas at the time: Westphalia, Eastphalia, Engria, and Nordalbingia in the north. Charlemagne's Frankish forces subdued Engria first. It was on this occasion that Charlemagne destroyed the Irminsul. The difficulty for the conqueror was that he had many campaigns not in Saxony, so that he would "lose ground" whenever he turned his attention to, say, Lombardy. Charlemagne would destroy Saxon strongholds and take hostages, but Saxons led by Widukind would raid Frankish lands while Charlemagne was away.
There were 18 separate campaigns between 772 and 804 needed to complete the absorption and Christianization of Saxony. During this phase he conquered Eastphalia and converted their leader Hessi in 775, then returned to Austrasia through Westphalia, leaving a few temporary strongholds there as well. At this point he felt Saxony was well in hand except for the northernmost section of Nordalbingia. More missionaries were sent by Charlemagne.
In 777, a diet at Paderborn was called to integrate Saxon and Frankish laws. Charlemagne earned the nickname "butcher of Saxons" by decreeing capital punishment for anyone engaging in heathen practices. His harsh approach put him at odds with Alcuin of York, whose position was that God's word should be spread by persuasion, not the sword. Two years later he enforced mass baptisms. There was relative peace at this time, the end of the first phase of the Saxon Wars.
In 782, the second phase would begin because Charlemagne couldn't leave well enough alone. We'll go further with this tomorrow.
As for that church at Deventer, it was rebuilt a few years after the destruction by the "Apostle of Saxony," St. Ludger.
