Bessas re-appears in 550, following the failure of a large Byzantine army under the "magister militum per Armeniam" Dagisthaeus to capture the strategic fortress of Petra in the ongoing war with the Persians over Lazica (western Georgia). To general surprise—and considerable criticism, in view of his advanced age and failure at Rome—Justinian named Bessas as Dagisthaeus' successor and entrusted him with the conduct of the war in Lazica.