There is a theory, already outlined by Toynbee, that empires that have succeeded one another in a dominant position are seeing their centre of gravity shift from east to west. This theory has most recently been evoked in connection with the replacement of the European empire by the American empire, which now seems to be giving way to an Asian empire.
If we want to analyse historically the mechanisms that lead an empire to its downfall, the best example to choose is undoubtedly that of the Eastern Roman Empire or Byzantine Empire in Western terminology. It is a world that has disappeared, but one that is close enough to us to allow us to understand it, and even to learn from its evolution, which only seems inevitable in retrospect. This story with its succession of internal and external causes of decline is summarized in the present study, leading to the disappearance of the Empire at the hands of the Ottoman dynasty. A parallel is drawn with the present situation of Europe.