ST. AMBROSE: Born around 338; died 397. Bishop of Milan, Italy. One of the four original Doctors of the Church.
Originally a government official, he became bishop in a most extraordinary way. While he was trying to keep the peace between opposing groups of Catholics and Arians who were vehemently disputing who should be the new bishop of Milan, the two groups began chanting that Ambrose should be the new bishop, though he was not yet baptized.
(The Arians felt that although Ambrose was Catholic in belief he would be a kinder bishop than they otherwise would likely get.)
He resisted strongly but eventually gave in and was baptized and ordained bishop.
Later, he assisted in the conversion of St. Augustine, to whom he gave the famous advice now paraphrased as "When in Rome, do as the Romans do."
To learn more about St. Ambrose and the early Church Fathers, you should get Jimmy Akin's best-selling book, The Fathers Know Best at http://jimmyakin.com/fathers