The Union of Active Struggle (ZWC) was a Polish national liberation and secret military movement that existed from June 1908 to 1914, when the ZWC formed the Polish Legion under Austria-Hungary during World War I. The ZWC was founded by Polish Socialist Party leaders Jozef Pilsudski, Marian Kukiel, Kazimierz Sosnkowski, and Wladyslaw Sikorski, and it carried out a campaign of bank and postal robberies, sabotage, and subversive destruction against the Russian Empire in Congress Poland.