Theodoric (Gothic Thiudareiks, meaning "King of the People") was born in 454, a year after the Ostrogoths had thrown off nearly a century of domination by the Huns. The son of the King Thiudimir, Theodoric went to Constantinople as a young boy, as a hostage to secure the Ostrogoths' compliance with a treaty Thiudimir had concluded with the Byzantine Empire.
He lived at the court of Constantinople for many years and learned a great deal about Roman government and military tactics, which served him well when he became ruler of his people. Treated with favor by the Emperors Leo I and Zeno, he became Magister militum (or Master of Soldiers) in 483 and one year later he became consul. He afterwards returned to live among the Ostrogoths when he was in his early twenties, and became their king in 488.
At the time, the Ostrogoths were settled in Byzantine territory as foederati (allies) of the Romans, but were becoming restless and increasingly difficult for Zeno to manage. Not long after Theodoric became king, the two men worked out an arrangement beneficial to both sides. The Ostrogoths needed a place to live, and Zeno was having serious problems with Odoacer, the King of Italy who had overthrown the western Roman Empire in 476. Ostensibly a viceroy for Zeno, Odoacer was menacing Byzantine territory and not respecting the rights of Roman citizens in Italy. At Zeno's encouragement, Theodoric invaded Odoacer's kingdom.
Theodoric came with his army to Italy in 488, where he won the battles at the Isonzo and at Milan in 489 and at the Adda in 490. In 493 he took Ravenna. Odoacer surrendered and was killed by Theodoric himself.
Like Odoacer, Theodoric was technically only a viceroy for the emperor in Constantinople. In reality, he was able to avoid imperial supervision, and dealings between the emperor and Theodoric were as equals. However, unlike Odoacer, Theodoric respected the agreement he had made and allowed Roman citizens within his kingdom to be subject to Roman law and the Roman judicial system. The Goths, meanwhile, lived under their own laws and customs.
Theodoric the Great was allied with the Franks by his marriage to Audofleda, sister of Clovis I, and with the Visigoths, Vandals and Burgundian kings. Clovis I's ambitions to also rule over the Goths brought on intermittent warfare between 506 and 523. For much of his reign, Theodoric was technically king of the Visigoths as well, becoming regent for an infant Visigothic king around 505. The Franks were able to wrest control of Aquitaine from the Visigoths in 507, but otherwise, Theodoric was able to defeat their incursions. Theodoric also stopped the Vandals from raiding his territories by threatening the weak Vandal king Thrasamund with invasion.
Theodoric was of Arian faith. At the end of his reign quarrels arose with his Roman subjects and the Byzantine emperor Justin I over the Arianism issue. Relations between the two nations deteriorated, although Theodoric's ability dissuaded the Byzantines from waging war against him. After his death, that reluctance faded quickly.
A fictionalized, but impressively researched, version of Theodoric's career is presented in Raptor, a novel by Gary Jennings.