In the next year, he served again under Belisarius in his new campaign against Sassanid Persia. On his own initiative, he led a force into the Persian rear, where he caught many Persians and their Arab allies out foraging. He killed some of them and captured others for interrogation. However, as he had acted without orders, Belisarius severely reprimanded him, and only through the mediation of Belisarius's co-commander Hermogenes were the two reconciled. At the Battle of Callinicum (April 19, 531), Sunicas and Simmas were placed in command of the Byzantine left. Although they repelled the successive Persian attacks, the remainder of the army was defeated and forced to withdraw. Sunicas and his men, mostly infantry, nevertheless continued to fight, preventing the Sassanid Persians from pursuing the defeated Byzantines. Nothing is known of him thereafter.