Flavius Valerius Leo (401 18 January 474), known in English as Leo the Thracian or Leo I, was a Byzantine Emperor who ruled from 457 to 474. He was known as Magnus Thrax (the "Great Thracian") by his supporters, and Macellus ("the Butcher") by his enemies.Ruling the Eastern Empire for nearly 20 years from 457 to 474, Leo proved to be a capable ruler, overseeing many ambitious political and military plans, aimed mostly for the aid of the faltering Western Roman Empire and recovering its former territories.