In the fall of 822, Lambert I of Nantes led the other counts of the Breton march against Wihomarc, but the resistance put up prevented him from being captured or killed.
For six weeks the Franks ravaged Brittany, but again Wihomarc did not give up and the army returned to Rouen in November.
According to Regino of Prüm, whose chronology is horribly inaccurate, Louis was defeated by the Bretons in 836, but it is the campaign of 824 which he probably has in mind.
[4] Both the Vita Hludowici and the Royal Frankish Annals mention the breadth and depth of the devastation of the imperial army, but ignore the ultimate success or lack thereof of the campaign; this probably indicates it was a setback.
[4] In May 825, Wihomarc led the other Breton leaders to Aachen to make peace with Louis, who pardoned them, granted them gifts, and made other concessions to them on the receiving of vows of loyalty.