Battle of the Catalaunian Plains
During Valentinian's reign the Huns invaded the Roman Empire. Eventually Aetius would defeat the Huns at the Battle of the Catalaunian Plains. Once the Huns returned, Pope Leo I and two other senators convinced Attila to leave. Valentinian himself killed Aetius, and in response Aetius's bodyguards assassinated Valentinian. Valentinian's reign was marked by the ongoing collapse of the western empire.