Kamenets-Podolsk (Kam'yanets'-Podil's'kyy), a city in the western Ukraine, then part of the Soviet Union, was occupied by German forces during the invasion of the Soviet Union in June 1941.
Shortly after Hungary (Germany's ally) declared war on the Soviet Union on June 27, 1941, officials of the agency responsible for 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. As a result, many Hungarian Jews who could not document their citizenship were also deported. Many Jewish communities, especially in the Transcarpathian Ukraine (then under Hungarian control), were deported in their entirety.
The Hungarians loaded Jews into freight cars and took them to Korosmezo, near the prewar Hungarian-Polish border, where they were transferred across the former Soviet border and handed over to the Germans. By August 10, 1941, approximately 14,000 Jews had been deported from Hungary to German-controlled territory. The Hungarian authorities transferred another 4,000 Jews later in the month. Once in German hands, the Jews, often still in family units, were forced to march from Kolomyja to Kamenets-Podolsk.
On August 27 and 28, detachments of Einsatzgruppen (mobile killing units) in Kamenets-Podolsk and troops under the command of the Higher SS and Police Leader for the southern region, SS General Friedrich Jeckeln, carried out mass killings of the Jewish deportees as well as the local Jewish population. According to Jeckeln's report, a total of 23,600 Jews were massacred in this action, the first large-scale mass murder in pursuit of the "Final Solution".