He was probably born in what is now Bulgaria, and a part of the Eastern Roman Empire (Constantinople still thought of itself as the Eastern Roman Empire; the Gothic wars were Justinian's attempt to re-unite with the Western Roman Empire). In his 20s he was a guardsman for Justinian, who at the time was not emperor but a prince and the nephew of Emperor Justin. Belisarius later was given the command to create a regiment of heavy cavalry armed with lances, bows, and long swords. This later grew to be 7000 men.
Although his early career saw him defeated many times, he retained Justinian's confidence. When Emperor Justin died in 527, Justinian took the throne and gave Belisarius command of the armies in the east. In the summer of 530, Belisarius managed an impressive defeat over the Sassanids (Persians) by digging trenches that forced the Persian cavalry into a vulnerable position. The Sassanid leader, King Kavad I, requested peace negotiations with the Byzantines.
A later loss to the Persians, however, caused him to be recalled to Constantinople and charged with incompetence.
Justinian was attempting some reforms against corruption that led ultimately to the Nika Riots, where Belisarius distinguished himself. They've been mentioned before, but it's time to explain how they came about, the intense rivalry between the Blues and the Greens, and the definitive way Belisarius dealt with the riots.
