Τοῦ δὲ Γρατιανοῦ τελευτήσαντος κατελείφθη βασιλεὺς αὐτοκράτωρ τῶν ἑσπερίων ὁ νέος Οὐαλεντινιανός, μήπω δὲ πρόσηβος γεγονώς. ὃς ὑποφθαρεὶς παρὰ τῆς μητρὸς Ἰουστίνης ἀρειανιζούσης τῷ τῶν ἀρειανῶν συνέθετο δόγματι καὶ τοῖς ὀρθοδόξοις ἀντέκειτο. ἐπαναστάντος οὖν αὐτῶ τοῦ Μαξίμου καὶ τυραννίδι ἐπιχειρήσαντος καὶ ἐν μάχαις ὑπερτερήσαντος, ἔγραψε πρὸς τὸν βασιλέα Θεοδόσιον τὰ συμβάντα, συμμαχίαν αἰτούμενος. κἀκεῖνος μὴ δεῖν θαυμάζειν ἀντέγραψεν εἰ ὁ δοῦλος ὑπερτερεῖ δεσπότου κατεξαναστὰς τοῦ τὸν οἰκεῖον ἀθετοῦντος δεσπότην καὶ κτίσμα καὶ δοῦλον καλοῦντος τὸν κτίστην, καὶ τῷ πατρὶ ὁμοούσιον καὶ ὁμότιμον. ἀπελθὼν δὲ εἰς συμμαχίαν αὐτοῦ τόν τε Μάξιμον συλλαβὼν ἀνεῖλε καὶ τὸν στρατηγὸν Ἀνδραγάθιον, ὃς ἐδολοφόνησε τὸν Γρατιανόν. εἶτ’ αὖθις Εὐγένιος ἐπανέστη κατὰ τοῦ νέου Οὐαλεντινιανοῦ καὶ τυραννίδι ἐπέθετο. φοβηθεὶς οὖν Οὐαλεντινιανὸς ἀγχόνῃ τοῦ βίου ἑαυτὸν ὑπεξήγαγε. καὶ μαθὼν τὴν Εὐγενίου τυραννίδα Θεοδόσιος ἐξεστράτευσε κατ’ αὐτοῦ. καὶ εἰς Θεσσαλονίκην ἐλθὼν μετὰ τοῦ στρατεύματος, ἐκεῖνος μὲν ὑβρίσθη ὑπὸ τῶν Θεσσαλονικέων, ὁ δὲ ἔπαρχος ἐφονεύθη, στασιάσαντος τοῦ δήμου δι’ αἰτίας τινάς. τότε μὲν οὖν ἐπὶ τῇ τοῦ λαοῦ κινήσει ἔδοξεν ἀνεξικακῆσαι ὁ βασιλεύς· μετὰ δὲ ταῦτα ἱππικὸν ἀγῶνα ἐκήρυξε, καὶ τοῦ λαοῦ ἀθροισθέντος ἐπὶ τὸ θέατρον περιέστησεν αὐτοῖς τὰ στρατεύματα, καὶ κατετόξευσαν τὸν δῆμον καὶ κατηκόντισαν, ὥστε θανεῖν ἐξ αὐτῶν ἄχρι τῶν πεντεκαίδεκα χιλιάδων. καὶ οὕτως ἐκπλήσας ὁ Θεοδόσιος τὸν θυμόν, ἐκεῖθεν ἀπάρας εἰς τὴν πόλιν τῶν Μεδιολάνων ἀφίκετο. ὅπου καὶ ἠλέγχθη παρὰ τοῦ μεγάλου Ἀμβροσίου καὶ εἰσελθεῖν εἰς τὴν ἐκκλησίαν οὐ συγκεχώρητο. καὶ οὐ πρότερον ἐφῆκεν αὐτῷ τὴν εἰς τὸ θεῖον θέμενος εἴσοδον, εἰ μὴ νόμον ἔθετο τὰς ψήφους τὰς φονικὰς μὴ πρότερον ἐκβιβάζεσθαι, πρὶν ἂν παρέλθοιεν μετὰ τὴν ψῆφον ἡμέραι τριάκοντα. τοῦτο δ’ ἐποίησε διὰ τὸ τοῦ βασιλέως ὀξύρροπον εἰς θυμόν, ἔνα διὰ τῶν τριάκοντα ἡμερῶν τοῦ θυμοῦ καταστορεννυμένου ἀπαθῶς ἐπισκέπτηται τἀς ψήφους καὶ τὰς μὲν ἐννόμους κυροῖ, τῶν δὲ δι’ ὀργὴν ἴσως ἐψηφισμένων ἀργίαν καταψηφίζηται. τῷ δὲ τυράννῳ Εὐγενίῳ συμμίξας ἐν ταῖς Γαλλίαις ὁ Θεοδόσιος νικᾷ αὐτὸν καὶ συλλαμβάνει καὶ ἀναιρεῖ.
(Joannes Zonaras, Epit. Hist. 13.18)
After Gratian had died, there remained as sovereign emperor of the West the young Valentinian, who was not yet an adolescent. Because his Arianizing mother Justina had corrupted him, he was in agreement with the dogma of the Arians and opposed the orthodox. Therefore, after Maximus had rebelled against him and made an attempt at usurpation, and had prevailed in battles, he, seeking a military alliance, wrote the sovereign Theodosius what had happened. The latter wrote back to him that there was no need for amazement if a slave rebelled and prevailed over a master when the latter was denying his own Master, calling the Creator a creation, a slave, and the same substance and same rank as the Father. After he had departed to assist him, he captured and killed Maximus and the general Andragathius, who had deceitfully murdered Gratian. Then, in turn, Eugenius rebelled against the young Valentinian and made an attempt at usurpation. Therefore, Valentinian, seized with fear, betook himself from life by hanging. Learning of Eugenius’ usurpation, Theodosius marched out against him. After he had reached Thessalonica with his army, he was insulted by the Thessalonicans and the prefect was murdered, the populace having rioted as a result of certain grievances. Now the sovereign then seemed to exhibit forbearance toward the populace’s action. But subsequently he announced an equestrian contest and, when the populace had gathered in the theater, the army surrounded them and with arrows and javelins shot the populace down, with the result that of them almost 15,000 died. After he had sated his anger in this fashion, Theodosius departed and went to the city of Mediolanum. There he was censured by Ambrose the Great and not allowed to enter the church. He did not permit him entrance to the divine precinct unless he enacted a law that capital sentences not be enforced until thirty days should elapse after the sentence. This he did on account of the sovereign’s predisposition toward anger, in order that, his anger being spread through the thirty days, he re-examine his sentences dispassionately and confirm the lawful but annul those that had perhaps been promulgated through rage. After he had engaged the usurper Eugenius in battle in Gaul, Theodosius defeated, captured, and killed him. (tr. Thomas N. Banchich & Eugene N. Lane)