He became a disciple of Hilary of Poitiers, a chief opponent in the West of the Arians, who denied the full deity of Christ, and who had the favor of the emperor Constantius. Returning to his parents' home in Illyricum, he opposed the Arians with such effectiveness that he was publicly scourged and exiled. He was subsequently driven from Milan, and eventually returned to Gaul. There he founded the first monastary in Gaul, which lasted until the French Revolution.
In 371 he was elected bishop of Tours. His was a mainly pagan diocese, but his instruction and personal manner of life prevailed. In one instance, the pagan priests agreed to fell their idol, a large fir tree, if Martin would stand directly in the path of its fall. He did so, and it missed him very narrowly. When an officer of the Imperial Guard arrived with a batch of prisoners who were to be tortured and executed the next day, Martin intervened and secured their release.
In the year 384, the heretic (Gnostic) Priscillian and six companions had been condemned to death by the emperor Maximus. The bishops who had found them guilty in the ecclesiastical court pressed for their execution. Martin contended that the secular power had no authority to punish heresy, and that the excommunication by the bishops was an adequate sentence. In this he was upheld by Ambrose, Bishop of Milan. He refused to leave Treves until the emperor promised to reprieve them. No sooner was his back turned than the bishops persuaded the emperor to break his promise; Priscillian and his followers were executed. This was the first time that heresy was punished by death.
Martin was furious, and excommunicated the bishops responsible. But afterwards, he took them back into communion in exchange for a pardon from Maximus for certain men condemned to death, and for the emperor's promise to end the persecution of the remaining Priscillianists. He never felt easy in his mind about this concession, and thereafter avoided assmblies of bishops where he might encounter some of those concerned in this affair. He died on or about 11 November 397 (my sources differ) and his shrine at Tours became a sanctuary for those seeking justice.