The paper examines a little-known unsuccessful attempt at a military coup in Poland in January 1919. The idea attracted notable members of the Polish National Committee, including Stanisław Grabski, and members of other right-wing organisations. Colonel Marian Januszajtis-Żegota took up the leadership at the military level, and Eustachy Sapieha at the political level. The coup was directed against the government led by the socialist Jędrzej Edward Moraczewski. The paper shows the political context of the uprising, the process, and the circumstances of its failure.