I believe it is a song about the fall of empire and the cyclical nature of power both interpersonal and global. It therefore works on a number of levels being historical - Decline of Roman empire, revolutionary takeover etc; as political commentary - China's supercedence of the us and the fall of that hegemony and yet can also work on a personal level I. E the breakdown of a relationship and the lows one can feel after the supreme high of being in love.