[4] Morman had been a faithful follower of Charlemagne, having sworn oaths to him and performed the giving of hands, probably becoming his vassus, although the Bretons rose up in rebellion in 811.
[5] Morman's rebellion against Frankish lordship in 814 threatened the integrity of Charlemagne's empire, recently inherited by Louis the Pious.
While the Bretons may have viewed the elevation of Morman as king on the death of Charlemagne as legitimate, the Frankish writers Astronomus and Ermold the Black saw it as a usurpation.
According to Ermold, the abbot asked, "Do you not remember your sworn fealty, or your right hand to the Franks / often given, and to Charles the service you showed?
"[7] After failing to bring Morman to accept Frankish rule through diplomacy, Louis prepared to invade Brittany.