On 24 July 840 in Strasbourg, Lothair precipitated a new civil war by declaring his imperium over all the lands of the empire and, joining with his nephew Pepin II of Aquitaine, attacked the Loire Valley. While Ermenaud III of Auxerre, Arnulf of Sens, Audri of Autun, and Gerard II of Paris pledged themselves for Lothair, Guerin and Adalbert of Avallon remained with Charles the Bald.
On 24 July 840 in Strasbourg, Lothair's actions led to a new civil war by declaring his authority over all the empire's territories and, joined by his nephew Pepin II of Aquitaine, attacking the Loire Valley. At the same time, Ermenaud III of Auxerre, Arnulf of Sens, Audri of Autun, and Gerard II of Paris pledged their allegiance to Lothair, whereas Guerin and Adalbert of Avallon remained loyal to Charles the Bald.