What is one strength and one weakness of the byzantine world in about 900 AD?

Well, I suppose the warriors were fierce. The Vikings of Beowulf's world were known to be ruthless in battle and without fear (except of scary dragons!) I think a weakness might have been its exclusively top down patriarchal power structure. Other than the king's command, there seemed to be no formal leadership among the soldiers. That would make their attacks rather chaotic but still violent.