It was General Belisarius. He was instrumental in helping Justinian in the campaign against the Sassanids where he won a victory against them in the Battle of Darra and the Battle of Callinicum during the Iberian War. He then led a campaign against the Vandals where he won the Battle of Ad Decimum and the Battle of Tricamarum. As a result the enemy surrendered and lost Roman territories were given back to the Byzantine Empire. He received many honors for his success on this campaign. He also led a campaign against the Ostrogoths but had to be recalled back to deal with threats from the Persians who conquered Syria.