Military Service and Captivity
According to the synaxarion, Peter was commissioned as an officer during the reign of the emperor Nikephoros (802–811) and shared in the Byzantine army's campaigns against Bulgaria. In one of these engagements the emperor was fatally wounded, and Peter was among the soldiers taken captive.
The tradition relates that, while he was in captivity, the Evangelist John the Theologian appeared to him during prayer one night and freed him. Released, Peter made his way back to Constantinople.