In spring 531, as news arrived of another Persian invasion, Hermogenes was sent again to the East at the head of reinforcements for Belisarius's army. He joined Belisarius, who had been following the Persians, at Barbalissus. There, Hermogenes mediated and resolved a dispute between Belisarius and one of his subordinate commanders, Sunicas. At this point the Persians, confronted by the Byzantine army, decided to withdraw. Hermogenes agreed with Belisarius's opinion that, their invasion having failed, they should be allowed to do so, but his subordinate commanders advocated battle. The two armies met near Callinicum, but the ensuing battle resulted in a heavy Byzantine defeat. In the aftermath of the battle, Hermogenes visited Kavadh as an envoy, but failed to achieve any results. He returned to Constantinople, from where he was again sent as an envoy in late summer of 531. There, he attached himself to the army of Sittas, and was with Sittas when he relieved the city of Martyropolis from a Persian siege.