“In order that the social crisis may bring about the proletarian revolution, it is necessary that, besides other conditions, a decisive shift of the petty bourgeois classes occurs in the direction of the proletariat. This gives the proletariat a chance to put itself at the head of the nation as its leader.”
Source: Fascism: What It Is and How to Fight It (1944), Ch. 3
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Leon Trotsky 106
Marxist revolutionary from Russia 1879–1940Related quotes

from "The Social-Democratic View of the National Question", 1904 (aged 26) http://www.marxists.org/reference/archive/stalin/works/1904/09/01.htm
Stalin's speeches, writings and authorised interviews

Source: The Birth of Fascist Ideology: From Cultural Rebellion to Political Revolution, 1994, p. 27

The Foundations of Leninism

Directives on the Cultural Revolution (1966-1972)

"Lessons of the Commune" http://www.marx.org/archive/lenin/works/1908/mar/23.htm, Collected Works, Vol. 13.
Collected Works

(1847)

Source: The Problems of Leninism, Ch.8

Source: Reform or Revolution (1899), Ch.8