451 What Happened in 451 AD F 1S 2S 3M 4T 5W 6T 7F 8S 9S 10M 11T 12W 13T 14F 15S 16S 17M 18T 19W 20T 21F 22S 23S 24M 25T 26W 27T 28F 29S 30 Apr 7 Attila the Hun plunders Metz in Northeastern France May 26 The Battle of Avarayr between Armenian rebels and the Sassanid Empire takes place. The Armenians are defeated militarily but are guaranteed freedom to openly practice Christianity. Jun 20 Battle of the Catalaunian Plains : Roman and Visigoths forces defeat Attila the Hun in north east France, halting Hun invasion of Roman Gaul (exact date disputed) Jun 24 10th recorded perihelion passage of Halley's Comet Oct 8 Council of Chalcedon (4th ecumenical council) opens - acts of second Council of Ephesus annulled and doctrine of Pope Leo's Tome adopted Jun 20 Theodoric I, King of the Visigoths (418-451), killed fighting the Huns. at the Battle of Châlons, dies at 60 or 61 [birth date uncertain]