The Secret History by Procopius

The people had since long previous time been divided, as I have explained elsewhere, into two factions, the Blues and the Greens.19 Justinian, by joining the former party, which had already shown favor to him, was able to bring everything into confusion and turmoil, and by its power to sink the Roman state to its knees before him. Not all the Blues were willing to follow his leadership, but there were plenty who were eager for civil war. Yet even these, as the trouble spread, seemed the most prudent of men, for their crimes were less awful than was in their power to commit. Nor did the Green partisans remain quiet, but showed their resentment as violently as they could, though one by one they were continually punished; which, indeed, urged them each time to further recklessness. For men who are wronged are likely to become desperate.

Then it was that Justinian, fanning the flame and openly inciting the Blues to fight, made the whole Roman Empire shake on its foundation, as if an earthquake or a cataclysm had stricken it, or every city within its confines had been taken by the foe. Everything everywhere was uprooted: nothing was left undisturbed by him. Law and order, throughout the State, overwhelmed by distraction, were turned upside down.