when they reigned with Christ.  The dragon was bound for a thousand years.  The Byzantine Empire ended the first beast, that was and is no more, and was ended by the second, that was yet to come.  Europe was protected and given valuable time to get its act together so that it was able to defend itself from the greatest threat to Christianity.  This empire had all the pieces and they all fit.  Prophecy fulfilled.  History is the only reliable method for interpreting it.