Sachsenkriege Karls des Großen
The former Frisian kingdom ("Magna Frisia") had been incorporated into Francia after the Frisian–Frankish wars, that ended with the victory of the Frankish troops led by "majordomo" Charles Martel at the Battle of the Boarn in 734. The remaining territory east of the Lauwers River was conquered by Charlemagne in the course of the Saxon Wars until 785.