Nazism was a form of Bolshevism turned against its initial form. - François Furet

To understand this relationship we may start with what has become an accepted observation: Stalinized Bolshevism and National Socialism constitute the two examples of twentieth-century totalitarian regimes. Not only were they comparable, but they form a political category of their own, which has become established since Hannah Arendt.

The American people were possessed by the capitalist spirit without ever having had a bourgeoisie; French political society, in contrast, created a bourgeoisie devoid of the capitalist spirit.

Fascism was born of the reaction of the particular against the universal, the national against the international. In its origins it was inseparable from Communism, fighting the latter’s goals even while adopting its methods… Communism and Fascism grew up on the same soil, the soil of Italian Socialism. The founder of the fasci in March 1919, Mussolini was a member of the revolutionary wing of the Socialist movement prior to supporting Italy's entry into the Great War; then, immediately afterward, he found himself in violent conflict with the Bolshevik-leaning leaders of his former party.