This article aims to show that as early as since 1945 the Yugoslav regime in Croatia and BiH was facing not only the active and passive resistance of individuals, but also an organised resistance of illegal groups of Croatian peasants, workers, high-school students and university students. As a rule, those groups were created spontaneously and always in response to foreignpolicy events and the internal political turmoil in Yugoslavia. In the first post-war years, the basic note in their political activities was the hope that the armed Crusader Movement would result in overthrowing the communist regime and establishing an independent Croatian state. When that hope came to nothing, the centre of illegal groups’ activities focused on political action and propaganda whose aim was to strip bare the communist regime and discredit yugoslavianism as an idea of statehood and nationality.