Simone Martini
St. Martin Renounces Weapons

St. Martin's Chapel, lower church, St. Francis of Assisi

In the Golden Legend the Emperor "Julian Caesar" is angered at his soldier Martin's refusal to take up arms. He resolves to send Martin into battle "protected and kept by the sign of the cross, and not by shield ne by helm." But in the morning the enemies send messengers announcing their surrender, "whereof it is no doubt but that by the merits of this holy man that this victory was had without shedding of blood."

Read more about images of St. Martin of Tours.
Also see this page for many more of Martini's St. Martin frescoes in the chapel.

Source: this page at Wikimedia Commons.