The three year Carolingian Civil War culminates in the decisive Battle of Fontenoy-en-Puisaye, also called the Battle of Fontenoy, fought at Fontenoy, near Auxerre, on June 25, 841.

The war is the contention over the territorial inheritances —the division of the unified lands of Charlemagne's Carolingian Empire between his grandsons, the three surviving sons of Louis the Pious.

Despite provisions by Louis the Pious, war breaks out between his sons and nephews.

It is a defeat for the allied forces of Lothair I of Italy and Pepin II of Aquitaine and a victory for Charles the Bald and Louis the German.

While hostilities continue until another two years into 843, the Treaty of Verdun ending the war shapes and influences history in Europe even to the present time.