The Fascist and Nazi dictatorships were children of the age of mass politics. They rested on mass mobilization and mass support. They claimed legitimacy as revolutionary incarnations of genuine democracy against the purportedly inauthentic, plutocratic, and decadent parliamentary regimes of the Western powers. The two dictatorships and the thirty years' war of 1914–45 that was their natural element illustrated the full extent to which the entry of the masses onto the stage of world history had failed to produce the universal peace that philosophers had foretold and optimists had celebrated. That regrettable circumstance was no surprise to perceptive students of the dictatorship and war without mercy that had attended the initial breakthrough of mass politics in Europe, the revolution in France that had begun in 1789. For as the visionaries of the tumultuous Assemblée Nationale that went to war against most of Europe in 1792–93 dimly perceived, mass politics had changed statecraft forever. It had fused foreign policy and domestic politics.

The Revolution overthrew both France's political order and its external relations. In seeking to reconstitute them, the revolutionaries concluded that they were “surrounded by snares and perfidy” and threatened by a “volcano of conspiracies about to erupt.”