Battle of Chalons: Flavius Aetius battles Attila the Hun. After the battle, which was inconclusive, Attila retreats, causing the Romans to interpret it as a victory.

The Battle of the Catalaunian Plains, also called the Battle of the Campus Mauriacus, Battle of Châlons, Battle of Troyes or the Battle of Maurica, took place on 20 June 451 AD, between a coalition, led by the Roman general Flavius Aetius and the Visigothic king Theodoric I, against the Huns and their vassals, commanded by their king, Attila. It proved to be one of the last major military operations of the Western Roman Empire, although Germanic foederati composed the majority of the coalition army. The exact strategic significance is disputed. Historians generally agree that the siege of Aurelianum was the decisive moment in the campaign and stopped the Huns' attempt to advance any further into Roman territory or establish vassals in Roman Gaul. However, the Huns looted and pillaged much of Gaul and crippled the military capacity of the Romans and Visigoths. Attila died only two years later, in 453. After the Battle of Nedao in 454, the coalition of the Huns and the incorporated Germanic vassals gradually disintegrated.