On other fronts, the Byzantine forces were also winning. The Persians and their Arab allies, with a mobile force of 15,000 high-quality cavalries, invaded Byzantine lands again, now via Euphratensis, a route they had never taken before. Belisarius was taken by surprise and was unsure whether this was a feint or a real attack, so at first, he did not move. He called upon Roman-allied Arab tribes for help and received 5,000 troops. He forced the Persians to retreat with a successful strategic maneuver but he kept pursuing the fleeing Persians, reportedly because his soldiers threatened mutiny if no battle was fought. With 20,000 Byzantines and 5,000 Arabs he moved against the Persians, but he was defeated by Callinicum (modern Raqqa) despite heavy numerical superiority, as the opposing commander, Azarethes, was a tactician as good as himself. Belisarius fled the field probably long before the fighting was over. This setback cost Justinian a chance to sign an early peace treaty as the shah regained confidence in the war effort. While the war went on after Dara and Callinicum, the death of the Persian shah, Kavad I, soon led to a peace treaty. The new shah, Khosrow, saw Justinian was anxious to sign for peace and thought he could quickly reach a favorable peace, such as the so-called eternal peace heavily favored the Persians. Belisarius was recalled to Constantinople and charged with incompetence and responsibility for the defeats at Thannuris and Callinicum, but after an investigation, the charges against him were cleared.