With a covert yet forceful intervention of the Comintern and the Soviet NKVD, Spain became for three years (1936-39) a laboratory of revolution where no tricks were considered too mean or too brutal.
While openly supporting a policy of non-intervention, Moscow secretly aimed at steering the Spanish Civil War towards a complete communist takeover. To that end, the ranks of the local communist party (PCE) were infiltrated by thousands of seasoned foreign "advisors" who quickly set in motion the liquidation of all "fascist" groups and "internal enemies" (social democrats, anarcho-syndicalists, Trotskyites, rebellious communists).
By using their bargaining power as the sole providers of weapons to the Republic, the communists acquired the liberty to create an extensive machinery of repression. Torture became systematic, summary executions a common practice. Before Franco's final victory in the civil war, thousands lost their life in these purges. But it would be incorrect to accuse only the Comintern and Stalin's NKVD henchmen in these atrocities.One of the leaders of the local PCE, Dolores Ibarrui, underlined the uncompromising nature of the whole revolutionary exercise by saying: "It is better to kill one hundred innocents than to let one guilty person go."
Communism is today still a noteworthy force in Spanish politics. Legalized in 1977, the PCE has now gradually accepted the democratic framework and distanced itself from its Marxist-Leninist past.