The dictatorship of the proletariat is class struggle waged by a proletariat that is victorious and has taken political power into its hands against a bourgeoisie that has been defeated but not destroyed, a bourgeoisie that has not vanished, not ceased to offer resistance, but that has intensified its resistance.
The dictatorship of the proletariat is a specific form of class alliance between the proletariat, the vanguard of the working people, and the numerous non-proletarian strata of the working people (petty bourgeoisie, small proprietors, the peasantry, the intelligentsia, etc.), or the majority of these strata, an alliance against capital, an alliance whose aim is the complete overthrow of capital, complete suppression of the resistance offered by the bourgeoisie as well as of attempts at restoration on its part, an alliance for the final establishment and consolidation of socialism.
It is a specific kind of alliance which takes shape in a specific situation, namely, amidst fierce civil war; it is an alliance between firm supporters of socialism and its vacillating allies, sometimes “neutrals” (in which case instead of an agreement on struggle the alliance becomes an agreement on neutrality); an alliance between economically, politically, socially, and spiritually different classes.
From: Deception of the People with Slogans of Freedom and..