 In addition to the other conquests , the Empire established a presence in Visigothic Hispania , when the usurper Athanagild requested assistance in his rebellion against King Agila I. In 552 , Justinian dispatched a force of 2 @,@ 000 men ; according to the historian Jordanes , this army was led by the octogenarian Liberius . The Byzantines took Cartagena and other cities on the southeastern coast and founded the new province of Spania before being checked by their former ally Athanagild , who had by now become king . This campaign marked the apogee of Byzantine expansion . 
