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Took place over the course of a week in Constantinople in 532 AD. It was the most violent riot of the time. Nearly half of the city was burned; tens of thousands of people were killed.
The riots started over a conflict about teams that competed in chariot racing. (The chariot racing team clubs were sort of a cross between political parties and street gangs. There were four groups: The Blues, Reds, Greens, and Whites, although the only teams with influence were the Blues (favored by Justinian I) and the Greens.
In 531, some members of the Blues and Greens had been arrested for and convicted of murder, because of crimes committed after chariot races. But a Blue and a Green escaped, and went to take refuge in the sanctuary of a church.
Justinian I was nervous--there were competitors for his throne, people were resentful over high taxes, they were very resentful over the attempts he had made to root out corruption and put in place reforms--and at the same time, he was negotiating with the Sassanids (Persians) to end the Iberian War (and reduce spending by the Eastern Roman Empire.)
He declared that a chariot race would be held on January 13, and he commuted the sentences to imprisonment, but the Blues and the Greens demanded that the two men be pardoned.
On the day of the chariot race, the Blues and Greens united--against Justinian. They chanted a unified Nika (meaning "Win!" or "Conquer!" Five days of rioting broke out--and local troops and police refused to kill their own neighbors. Justinian had to use mercenaries to put down the riots, in part by appealing to the Blues by (1) reminding them of his prior support (2) pointing out that the emperor who would take his place was a Green and (3) bribing them with gold.
The Hagia Sophia, the largest church in Constantinople (and until 1520, the largest cathedral in the world) was destroyed (Justinian would rebuild it about four years later.)
To some degree, this incorporated the timeless poor versus rich distinction, as well as resistance to a ruler who was trying to root out corruption.
What was the Nika Revolt?