The aim of this article is to identify and characterize selected sources of national antagonisms of the Second Polish Republic through Ukrainian activities in Eastern Lesser Poland. The considerations are based on archival material and critical analysis of scientific literature.
A thesis was put forward that the actions taken to materialize the Ukrainian case and interests in Eastern Lesser Poland were a source of national antagonisms in the Second Polish Republic and one of the factors weakening the security of the Polish state.
The presented arguments show that the so-called Ukrainian case in Eastern Lesser Poland was connected to the security of the Second Polish Republic, and the Ukrainian actions in this region, unfavourable towards Poland, weakened Poland’s security. The actions taken by the Ukrainians were a source of national antagonisms in Poland in the interwar period. Nationalism, terrorism, neglect of duties related to military service, anti-Polish propaganda and defamation of Poland in the Ukrainian press and diplomacy in the international arena, threatened Poland’s security in relation to the development of the sociopolitical situation in Eastern Lesser Poland.