Battle of Pharsalus
What little is known of Petro comes from Suetonius, who says that he was a native of Reate in Latium, and had been one of the loyal soldiers of Pompeius during the Civil War, and might have been a centurion. He escaped capture after the final defeat of the Pompeians at the Battle of Pharsalus in 48 BC, and returned home, eventually receiving Caesar's pardon. He became a , a collector of taxes on behalf of the Roman Republic.