Sachsenkriege Karls des Großen
The conversion of the Old Saxons was imposed by armed force and successfully completed by Charles the Great (Charlemagne) and the Franks in a series of campaigns (the Saxon Wars), starting in 772 with the destruction of their Irminsul and culminating in the defeat and massacre of Saxon leaders at the Massacre of Verden in 787 and the subjugation of this large tribe by forced population movements of Saxons into Frankish territory and vice versa.