The Ustaše , also known as "Ustashe", "Ustashas", and "Ustashi", were members of the Ustaša – Croatian Revolutionary Movement , a Croatian fascist, ultranationalist and terrorist organization, active, in its original form, between 1929 and 1945. Its members murdered hundreds of thousands of Serbs, Jews, Roma (Gypsies) and anti-fascist or dissident Croats in Yugoslavia during World War II.