Leo I., who reigned at Constantinople from 457 to 474, and who was therefore Emperor during the whole time that Theodoric dwelt there as hostage, was not, as far as we can ascertain, a man of any great abilities in peace or war, or originally of very exalted station. But he was "curator" or steward in the household of Aspar, the successful barbarian adventurer who has been already alluded to.[34] As an Arian by religion, and a barbarian, or the son of a barbarian, by birth, Aspar could not himself assume the diadem, but he could give it to whom he would, and Leo the steward was the second of his dependants whom he had thus honoured. Once placed upon the throne, however, Leo showed himself less obsequious to his old master than was expected. The post of Prefect of the City became vacant; Aspar suggested for the office a man who, like himself, was tainted with the heresy of Arius. At the moment Leo promised acquiescence, but immediately repented, and in the dead of night privately conferred the important office on a Senator who professed the orthodox faith. Aspar in a rage laid a rough hand on the Imperial purple, saying to Leo: "Emperor! it is not fitting that one who wears this robe should tell lies". Leo answered with some spirit: "Neither is it fitting that an Emperor should be bound to do the bidding of any of his subjects, and so injure the State".
After this encounter there were thirteen years of feud between King-maker and King, between Aspar and Leo. At length in 471 Aspar and his three valiant sons fell by the swords of the Eunuchs of the Palace. The foul and cowardly deed was perhaps marked by some circumstances of especial cruelty, which earned for Leo the title by which he was long after remembered in Constantinople, "The Butcher".[35]
In order to strengthen himself against the adherents of Aspar, Leo cultivated the friendship of a set of wild, uncouth mountaineers, who at this time played the same part in Constantinople which the Swiss of the Middle Ages played in Italy. These were the Isaurians, men from the rugged highlands of Pisidia, whose lives had hitherto been chiefly spent either in robbing or in defending themselves from robbery. At their head was a man named Tarasicodissa,--probably well born, if a chieftain from the Isaurian highlands could be deemed to be well born by the contemptuous citizens of Constantinople, no soldier, for we are told that even the picture of a battle frightened him, but a man whom the other Isaurians seem to have followed with clannish loyalty, like that which the Scottish Camerons showed even to the wily and unwarlike Master of Lovat.