"After failing to bring Morman to accept Frankish rule through diplomacy, Louis prepared to invade Brittany.In the spring of 818, Louis's army, composed of forces from all the Frankish "regna" (literally "kingdoms", but actually subkingdoms), assembled at Vannes, the westernmost point of actual Frankish control, and marched to Priziac in the far west of the county of the Vannetais on the bank of the river Ellé.