SAINT AMBROSEBishop and Doctor of the Church(c. 339 – 397)
Ambrose was of a noble family, and was governor of Milan in 374, when a bishop was to be chosen for that great see. As the Arian heretics were many and fierce, he was present to preserve order during the election. Though only a catechumen, it was the will of God that he should himself be chosen by acclamation; and, in spite of his utmost resistance, he was baptized and consecrated.
He was unwearied in every duty of a pastor, full of sympathy and charity, gentle and condescending in things indifferent, but inflexible in matters of principle. He showed his fearless zeal in braving the anger of the Empress Justina, by resisting and foiling her impious attempt to give one of the churches of Milan to the Arians, and by rebuking and leading to penance the really great Emperor Theodosius, who in a moment of irritation had punished most cruelly a sedition of the inhabitants of Thessalonica.
He was the friend and consoler of St. Monica in all her sorrows, and in 387 he had the joy of admitting to the Church her son, St. Augustine.
St. Ambrose died in 397, full of years and of honors, and is revered by the Church of and as one of her greatest doctors. Lives of the Saints, by Alban Butler, Benziger Bros. ed.  In other years: St Ambrose of Milan (340? – 397)He was born in Trier (now in Germany) between 337 and 340, to a Roman family: his father was praetorian prefect of Gaul. Ambrose was educated at Rome and embarked on the standard cursus honorum of Roman advocates and administrators, at Sirmium, the capital of Illyria. In about 372 he was made prefect of Liguria and Emilia, whose capital was Milan.
In 374 the bishopric of Milan fell vacant and when Ambrose tried to pacify the conflict between the Catholics and Arians over the appointment of a new bishop, the people turned on him and demanded that he become the bishop himself. He was a layman and not yet baptized (at this time it was common for baptism to be delayed and for people to remain for years as catechumens), but that was no defence. Coerced by the people and by the emperor, he was baptized, ordained, and installed as bishop within a week, on 7 December 374.
He immediately gave his money to the poor and his land to the Church and set about learning theology. He had the advantage of knowing Greek, which few people did at that time, and so he was able to read the Eastern theologians and philosophers as well as those of the West.
He was assiduous in carrying out his office, acting with charity to all: a true shepherd and teacher of the faithful. He was unimpressed by status and when the Emperor Theodosius ordered the massacre of 7,000 people in Thessalonica, Ambrose forced him to do public penance. He defended the rights of the Church and attacked the Arian heresy with learning, firmness and gentleness. He also wrote a number of hymns which are still in use today.
He died on Holy Saturday, 4 April 397. See the article in the Wikipedia.
Ambrose was a key figure in the conversion of St Augustine to Catholicism, impressing Augustine (hitherto unimpressed by the Catholics he had met) by his intelligence and scholarship.