[2][3][4] Warski was active in the communist movement from 1889, when he co-founded the Union of Polish workers, with Julian Marchlewski and Bronislaw Wesolowski.

In 1893, he was one of the four founders of the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL), with Rosa Luxemburg, Leo Jogiches, and Marchlewski.

After the failure of the 1923 communist uprising in Germany, and similar but smaller-scale disturbances in Poland, the three Ws vigorously defended the leaders of the German party, who were accused of passivity, and as a power struggle developed in the Kremlin between during Lenin's terminal illness, pitching Joseph Stalin and the chairman of Comintern, Grigory Zinoviev against Trotsky, they issued a statement in December 1923 declaring that the name of comrade Trotsky is for our party, for the whole International, for the whole revolutionary world proletariat, indissolubly bound up with the victorious October Revolution.

The record of the Polish leadership was subjected to a three-day examination during the Fifth Comintern Congress in June 1924, chaired by Stalin, after which Warski capitulated and wrote a recantation, published in Pravda in January 1925.

In June 1937, the head of the NKVD, Nikolai Yezhov told a plenum of the Central Committee that the police had uncovered a 'Polish Military organisation', whose members had infiltrated the USSR by posing as political refugees.