The Mad Monarchist: Lessons from Honorius: It was on this day in 393 AD that Emperor Theodosius the Great proclaimed his son Honorius "co-emperor" of the Roman Empire. Honorius was only eight-years old at the time but he would go on to have one of the most disastrous reigns in Roman imperial history, a far cry from that of his father. Emperor Theodosius had reunited the Roman world, being the last caesar to rule both east and west, defended the frontiers, established Christianity as the official religion of the Roman Empire and generally had quite a glorious reign. Emperor Honorius, on the other hand, would preside over the first sacking of Rome by the barbarian hordes when Alaric the Visigoth captured the Eternal City in 410 AD. How could this have happened?