Long Walls
It is likely that the close trust he shared with Maurice dates from the latter's time as commander of the "Excubitores", before his ascension to the throne. Throughout his career, Comentiolus would be loyal to Maurice, and the Emperor would watch over his protégé's career. The next year, after a truce with the Avars had been arranged, he was appointed in charge of a regiment ("taxiarchia") operating against the Slavic tribes that raided Thrace and had penetrated as far as the Long Walls of Anastasius, Constantinople's outer defensive system. Comentiolus defeated them at the river Erginia, near the Long Walls. As a reward for this success, he was appointed "magister militum praesentalis" in 585.