eight years of age, he was taken hostage in Constantinople to secure the Ostrogoths' compliance with a treaty Theodemir had concluded with the augustus Leo I (ruled 457–474). The treaty secured a payment to Constantinople of some 300 pounds' worth of gold each year. Theodoric was well educated by Constantinople's best teachers. His status made him valuable, since the Amal family from which he came (as told by Theodoric), allegedly ruled half of all Goths since the third century AD. Historian Peter Heather argues that Theodoric's claims were likely self-aggrandizing propaganda and that the Amal dynasty was more limited than modern commentators presume. Until 469, Theodoric remained in Constantinople where he spent formative years "catching up on all the Romanitas" it had taken generations of Visigothic Balthi to acquire. Theodoric was treated with favor by the emperor Leo I. He learned to read, write and perform arithmetic while in captivity in the Eastern Empire. When Leo heard that his imperial army was retreating from the Goths near Pannonia, he sent Theodoric home with gifts and no promises of any commitments. On his return in 469/470, Theodoric assumed leadership over the Gothic regions previously ruled by his uncle, Valamir, while his father became king. Not long afterwards near Singidunum (modern Belgrade) in upper Moesia, the Tisza Sarmatian king Babai had extended his authority at Constantinople's expense. Legitimizing his position as a warrior, Theodoric crossed the Danube with six thousand warriors, defeated the Sarmatians and killed Babai; this moment likely crystallized his position and marked the beginning of his kingship, despite not actually having yet assumed the throne. Perhaps to assert his authority as an Amali prince, Theodoric kept the conquered area of Singidunum for himself. Throughout the 470s, sometimes in the name of the empire itself, Theodoric launched campaigns against potential Gothic rivals and other enemies of the Eastern Empire, which made him an important military and political figure. One of his chief rivals was the chieftain of the Thracian Goths Theodoric Strabo (Strabo means "the Squinter"), who had led a major revolt against the emperor Zeno. Finding common ground with the emperor, Theodoric was rewarded by Zeno and made commander of East Roman forces, while his people became foederati or federates of the Roman army. Zeno attempted to play one Germanic chieftain against another and take advantage of an opportunity sometime in 476/477 when—after hearing demands from Theodoric for new