By what treaty was Charlemagne's empire divided among his grandsons?

The Treaty of Verdun divided Charlemagne’s empire among his grandsons. Signed in 843, it ended a civil war between the three surviving sons of Louis the Pious: Lothair I, Louis the German, and Charles the Bald.

The settlement split the Carolingian Empire into West Francia, Middle Francia, and East Francia. West Francia became the nucleus of medieval France, while East Francia developed into the basis of the German kingdom. Lothair received the central territory and retained the imperial title.

The treaty followed the Battle of Fontenoy in 841 and the Strasbourg Oaths in 842. It was the first of several partitions that progressively weakened the unified empire created by Charlemagne.

A common mix-up is confusing Verdun with the later treaties of Prüm, Meerssen, and Ribemont. Those later agreements adjusted or divided parts of the Carolingian kingdoms; Verdun was the major three-way partition in 843.