The Roman Empire had difficulty responding to all the barbarian raids, and Flavius Aëtius had to use these tribes against each other in order to maintain some Roman control. He first used the Huns against the Burgundians, and these mercenaries destroyed Worms, killed king Gunther, and pushed the Burgundians westward. The Burgundians were resettled by Aëtius near Lugdunum in 443. The Huns, united by Attila, became a greater threat, and Aëtius used the Visigoths against the Huns. The conflict climaxed in 451 at the Battle of Châlons, in which the Romans and Goths defeated Attila.