 This time emperor Louis responded quickly, and soon the younger Louis was forced into the far southeastern corner of his realm, the March of Pannonia.Peace was then made by force of arms.When the emperor Louis died in 840, and Lothair I claimed the whole Empire, Louis allied with Charles the Bald, and defeated Lothair I and their nephew Pepin II of Aquitaine, son of Pepin I of Aquitaine, at the Battle of Fontenoy in June 841.