Born to pagan parents; his father was a Roman military officer and tribune. Martin was raised in Pavia, Italy. Discovered Christianity, and became a catechumen in his early teens. Joined the Roman imperial army at age 15, serving in a ceremonial unit that acted as the emperor's bodyguard, rarely exposed to combat. Cavalry officer, and assigned to garrison duty in Gaul.
Trying to live his faith, he refused to let his servant to wait on him. Once, while on horseback in Amiens in Gaul (modern France), he encountered a beggar. Having nothing to give but the clothes on his back, he cut his heavy officer's cloak in half, and gave it to the beggar. Later he had a vision of Christ wearing the cloak.