I am particularly interested in Rome, and most curiously, England. Also, is there a common, causal thread through the failure of all of the Great Empires in time? Middle Kingdom China, Assyria, Babylon, Egypt, Spartica Greece, Persia, Rome, Napoleonic France, England....America. Why do Empires burn out, wilt and fall? If you had to pick one, specific, greatest cause, what would it be? I claim that Empire is an unsustainable 'condition.' To be an Empire, a nation-state has to project power, thwart enemies, conquer and rule for its own necessities. An Empire has to cull, harvest, tax and impose its will and project its authority, whether by force or culture. Anything less, and the decay has already begun. An Empire is no longer an Empire the moment it loses forward momentum in its quest for growth of wealth and power. An Empire is, ipso facto, a predetermined period of time, whether 3,000 years, or 100.