Disappointed by Shahrbaraz's failure, Khosrow II sent a messenger bearing a letter to Kardarigan, who was the second-in-command of the Sasanian army. The letter said that Kardarigan should kill Shahrbaraz and take his army back to Ctesiphon, but the bearers of the letter were intercepted in Galatia by Byzantine soldiers, who gave the letter to the future emperor Constantine III who in turn gave it to Heraclius. After reading the letter, he offered to show the letter to Shahrbaraz in a meeting at Constantinople. Shahrbaraz accepted his proposal and met Heraclius at Constantinople, where he read the letter and switched over to Heraclius' side. Shahrbaraz then changed the contents of the letter, making it state that Khosrow II wanted 400 officers killed, ensuring that Kardarigan and the rest of the army remained loyal to him.