Battle of Fontenoy
841 CE.
Shown on the map at 47.650°, 3.300°.
The Battle of Fontenoy (25 June 841), also called the Battle of Fontenoy-en-Puisaye or Battle of Fontenay in older works, was the largest battle of the Carolingian civil war. Fought at Fontenoy in the Puisaye, the battle was a major 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. It was not, however, decisive. Hostilities dragged on for another two years until the Treaty of Verdun.
Text from the Wikipedia article Battle of Fontenoy (841), licensed CC BY-SA 4.0.