Annales regni Francorum
According to the "Royal Frankish Annals", the Franks campaigned in Saxony in 772, when Charlemagne ordered the destruction of the Irminsul sanctuary. The Saxon Wars continued when Westphalian tribes devastated the church of Deventer and the Angrarii laid siege to the Frankish court at Fritzlar. The king retaliated against the local nobility, enforcing the decree to incorporate the Saxon lands as a Frankish march.