The great Byzantine general Belisarius on Justinian's right
Thanks for posting the famous mosaic. Unfortunately, the claim that Belisarius is the man on Justinian’s right is only a guess. It’s a fairly logical guess, given what we know about what Belisarius looked like (dark hair and beard according to Procopius). However, I think the mosaic was done during a time when Belisarius was in semi-disgrace and Justinian was always fretful of his great general’s popularity in Italy. Really, it could be any one of Justinian’s top ministers—maybe his nephew Germanus who was married to a Gothic princess.