After this troubles crowded thick and fast on the bishop. Gratian, whom he had loved as a son, was treacherously murdered in Gaul by order of Maximus, who had been given by Gratian himself rule over the prefecture of Gaul with the title of emperor. The grief of Ambrose was deep; but besides he was forced to act for Gratian's half-brother Valentinian, whose mother Justina never failed to send for the bishop to help her out of her difficulties, and directly he had made things smooth, proceeded to fall back into them. Thankful indeed was he when she and her son set out for Thessalonica, to put themselves under the protection of Theodosius. In the long line of the emperors of the East there were few more honest and able than Theodosius. He found his dominions in a state of confusion, the prey of the barbarian hordes that were always pouring westwards from the wide plains of Scythia, while internally the strife in the church was fiercer than ever. Quietly and steadily the emperor took his measures. Here he pardoned, there he punished, and men felt that both pardon and punishment were just. He was not yet strong enough to fight against the rebel Maximus, as he would have liked to do, but he determined that, cost what it might, he would never forsake the young Valentinian. Maximus had snatched at some excuse to invade Milan, which on his entrance he had found abandoned by its chief men, save only Ambrose, who treated him with contempt and went his own way. The intruder's efforts to buy support by conciliation failed miserably, and in a few weeks there came the news that Theodosius was preparing to meet him on the borders of Hungary, or Pannonia. Then Maximus assembled what forces he could, and set out across the pass of the Brenner. Two battles were lost, for the legions of Maximus were but half-hearted; in the third he was taken prisoner and brought before the emperor. Theodosius was a merciful man, but his heart was hard towards the murderer of Gratian. 'Let him die!' he said, and without delay the order was carried out. [Illustration: 'Let him die!' he said.] Now that Maximus was dead the legions were quite ready to return to their rightful emperor, and as soon as he had settled matters Theodosius went on to Milan. There he and Ambrose became great friends; the bishop was much the cleverer of the two, but they were both honest and straightforward, with great common-sense, and it must have been a relief to Ambrose, who did not in the least care for being an important person, to feel that he could at last mind his own business, and leave affairs of state to the emperor. It was while all seemed going so smoothly that the supreme crisis in the lives of both men took place--the event which has linked the names of Ambrose and Theodosius for evermore.