Combat Organization of the Polish Socialist Party

Postcard released by PPS around 1905–1907. Text in top left corner: 'Fighters for freedom'. Tombstones have names of PPS members who died in recent actions.

The Combat Organization of the Polish Socialist Party (Polish: Organizacja Bojowa Polskiej Partii Socjalistycznej, abbreviated OBPPS) was an illegal Polish guerrilla organization founded in 1904 by Józef Piłsudski.^{[citation needed]}

Its operations reached their zenith about 1904–1908, when it numbered over 2,000 members, including over 700 paramilitary personnel, and carried out over 2,500 operations. The organization had over 5,000 members at the height of its power. Afterwards it declined and was dissolved in 1911. Its goal was to create an armed resistance movement against the Imperial Russian authorities in partitioned Poland. Its most notable operations included the Bloody Wednesday of 15 August 1906; the failed assassination attempt against the Governor-General of Warsaw, Georgi Skalon, 18 August 1906; and Bezdany raid, a major train robbery, 26 September 1908.