While much of his support from the people came from his popularity and reverence paid to him, he also built upon these associations with the poor and with introduction of popular reforms in the order and manner of public worship. He also preached on the public characters of his time, in which the applause of the people was often mingled with derision of the imperial court. While the court was often displeased with his religious positions and his conduct, they respected his political talents and when the need arose, they solicited his aid which he generously granted. Thus, when Magnus Maximus usurped power in Gaul and was considering entering Italy, Valentinian asked Ambrose to go to Gaul and dissuade him from doing so. Ambrose's journey was successful. In a second try for mediation, Ambrose was not as successful as his advice was not followed, allowing Maximus to enter Italy and take Milan. While Justina and her son fled, Ambrose remained in Milan and attended to many of those who suffered from the invasion.
In the power struggles of the late fourth century, [[Theodosius the Great|Theodosius I]], emperor of the East, came to be in undisputed possession of the Roman empire. Yet, Ambrose chastised Theodosius for a massacre in Thessalonica, bidding him to emulate [[David]] in repentance. Also, he encouraged Theodosius in the enactment of the "Theodosian decrees" which were more characteristic of Ambrose agenda that that of Theodosius. After the defeat of Eugenius he asked for pardon of those who supported Eugenius. Ambrose passed away on [[April 4]], 397, two years after the death of Theodosius. Ambrose's successor as bishop of Milan was Simplician.
Ambrose is ranked with the great Western Christian leaders of the time: Augustine, St. [[Jerome]], St. [[Gregory the Great]], and St. [[Hilary of Poitiers]]. Ambrose was most known for his administrative talents, given his education and early experience before becoming a bishop. Yet, like Hilary he was an Alexandrian and was in the forefront in the doctrinal issues of the day, particularly those concerning Arianism. His sermons were famous and were influential in the conversion of Augustine. His endeavors in [[hymnography|hymn writing]] became models of hymns of dignified simplicity for future times. Ambrose is credited with introducing [[antiphonal chant]]ing wherein one choir alternates with another. Of particular note is that Ambrose baptized Augustine, his celebrated convert.