From Soldier to Monk
According to the synaxarion, Peter was the son of Theophilos and Eudokia and bore the lay name Leo. He distinguished himself in the Byzantine military and was made a count by the emperor, owing to his bodily strength and skill in warfare.
After many years of valor in battle, he renounced everything and became a monk, entering a monastery known as Daphnon and changing his name from Leo to Peter. This turn from a celebrated martial career to monastic obedience is the central note of his commemoration as a model of repentance and perseverance.