In the year 390, after the murder of one of his generals in Thessalonica, the Christian emperor of Rome Theodosius I (born January 11, 347; died January 17, 395) ordered a brutal retaliation. A chariot race was announced, but after townspeople arrived to watch, they were locked in the stadium and attacked by imperial soldiers. Within three hours, 7,000 citizens were dead.Ambrose, bishop of Milan, felt constrained to protest, and in so doing initiated a way of looking at Christianity and politics that would influence the Roman Empire into the Middle Ages. He wrote a letter to Theodosius, which reads in part: "What, then, could I do? Should I not hear? But I could not close my ears. … Should I keep silence? But then my conscience would be bound, my speech taken away, which would be the most wretched condition of all. And where would be that text? If the priest does not speak to someone who errs, he who errs will die in his sin, and the priest will be liable because he failed to warn the errant man." Ambrose then recalls the story of Nathan confronting David, as well as other biblical passages on repentance.The bishop had good reason to believe his letter would find its mark in the emperor's heart. Theodosius had been raised in a Christian family, was the first emperor to decline the title pontifex maximus (supreme guardian of the Roman cults), and believed the Nicene Creed. He went so far in his support of the creed, as well as in his opposition to paganism and Arianism, to make its tenets binding: all the empire's subjects were mandated to recognize the Father, Son, and Holy Spirit of one substance, and practice "that religion that Peter the Apostle transmitted to the Romans." And Theodosius had accepted Ambrose's authority ...