In 1923, Kozovski was among the leaders of the quickly-crushed June Uprising, a chaotic agrarian uprising against the right-wing 9 June coup d'état; he also participated in the better-organized communist September Uprising of the same year. After that uprising's suppression, Kozovski was forced to emigrate to the Soviet Union, where he graduated from the M. V. Frunze Military Academy and became a reader of military science at the Communist University of the National Minorities of the West.