Battle of the Catalaunian Plains
The Visigoths with their capital at Toulouse, remained "de facto" independent, and soon began expanding into Roman territory at the expense of the feeble Western empire. Under Theodoric I (418–451), the Visigoths attacked Arles (in 425 and 430) and Narbonne (436), but were checked by Flavius Aetius using Hunnic mercenaries, and Theodoric was defeated in 438. By 451, the situation had reversed and the Huns had invaded Gaul; now Theodoric fought under Aetius against Attila the Hun in the Battle of the Catalaunian Plains. Attila was driven back, but Theodoric was killed in the battle.