St. Martin was born in Pannonia (now Hungary), joined the Roman army and served in Italy and then in Gaul, where the famous episode of his ‘charity’ took place. One winter day in 337 he met a beggar shivering with cold. Martin cut his cloak in two and handed one to the pauper. At night he saw a dream, in which Christ, wearing the half of his cloak came and thanked him. Martin left the Roman army and converted to Christianity. He founded a monastery of Liguge in Poitou, in 370 he was elected bishop of Tours. Until his death in 397 he fulfilled his Episcopal functions, worked as a missionary throughout western France. He founded the monastery of Marmoutier, which became one of the largest abbeys in the west. His religious work gave him the name Apostle of the Gauls.
St. Martin is a patron saint of soldiers and knights, as well as of drapers, furriers and tailors. He is also one of the patrons of French monarchy.
See: Anthony van Dyck St. Martin Dividing His Cloak.
Jean Fouquet St. Martin.
El Greco St. Martin and the Beggar, St. Martin and the Beggar.
Masolino St. John the Evangelist and St. Martin of Tours.
Simone Martini. St. Martin is Dubbed a Knight, St. Martin  Renounces of Arms,St. Martin and the Beggar,St. Martin's Dream, Death of St. Martin.

Recommended reading:
The Book of Saints: The Lives of the Saints According to the Liturgical Calendar by George Angelini, Victor Hoagland (Editor). Regina Press, Malhame & Company, 1986.
365 Saints: Your Daily Guide to the Wisdom and Wonder of Their Lives by Woodeene Koenig-Brick (Author). Harper SanFrancisco, 1995.