Byzantine Military Tactics

OK, it's really not THAT much of a stretch from medicine to killing - wounds, etc., right? Check out this link - it's terrific. Medievalists.net is a newsletter full of articles and things for us - medievalists. They have a great article on Byzantine military tactics, which the Normans either appropriated (I'm thinking specifically here of Robert Guiscard, but they all did it) or, is this more interesting - did the Byzantine Emperor learn this from his Varangian Guard?