I'd read somewhere that the downfall of fascism is always on the battlefield. Fascism simultaneously requires that a large population believe they are a persecuted group in danger of extinction (else there's no reason to subjugate one's individual will & liberty to a strong leader) and that they are superior to those who oppose them (else their cause is futile and they ought to ally themselves with the superior force). The distortions in reality needed to justify these contradictory beliefs filter up into the leaders' decision-making itself, such that they eventually make stupid decisions like bombing Pearl Harbor or opening a second front in the European war.