The city of Kamianets-Podilskyi (Kam'yanets'-Podil's'kyy), now in south-western Ukraine, was part of the Ukrainian SSR invaded by German forces on June 22, 1941 during the opening stages of Operation Barbarossa launched from occupied Poland. Shortly after Hungary (Germany's ally) engaged in war on the Soviet Union on June 27, 1941, officials of the agency responsible for the foreign nationals living in Hungary decided to deport foreign Jews; these were mostly Polish and Russian Jews, but there were also many refugees from western Europe. Jews who could not readily establish Hungarian citizenship were equally vulnerable to deportation.