In late antiquity, relations between peoples and the Roman Empire are ambivalent. The allies are potentially enemies and vice versa, with each context its alliances.
However in 451 AD the federated peoples of the western empire will answer the call of Aetius, Magister Utriusque Militiae, to stop a great threat: The incursion of Attila, chief of the Huns, and his allies within the empire.
A gigantic battle ensues in two steps: Orleans on June 14 and then in the surroundings from Troyes on June 20. We call this last battle « Battle of the Catalaunian Plains » (Campus Mauriacus), supposed place of the conflict.
If the Roman Empire is often presented as a winner, the two belligerents come out of it very weak. Thus the Hunnic Empire will disappear 3 years later as well as Attila and Aetius and the Western Roman Empire will collapse 25 years later, consensus date to designate the end of antiquity.
Conversely the former federates consolidate their places in the world and will continue to write history.