 Events of the later years of the reign showed that Constantinople itself was not safe from barbarian incursions from the north , and even the relatively benevolent historian Menander Protector felt the need to attribute the Emperor 's failure to protect the capital to the weakness of his body in his old age . In his efforts to renew the Roman Empire , Justinian dangerously stretched its resources while failing to take into account the changed realities of 6th @-@ century Europe . Paradoxically , the grand scale of Justinian 's military successes probably contributed in part to the Empire 's subsequent decline . 
