The Holocaust originated in Nazi Germany during the late-1930s and quickly spread throughout Central and Eastern Europe. As the country responsible for conceptualizing and carrying out the systematic extermination of Europe's Jewish population, Germany was the core of that effort, and its scale expanded in direct relation to the reach of the German Army and associated extermination units, especially the Einsatzgruppen units and, more specifically, the Schutzstaffel (SS) units that were formed and tasked with the mission of locating and killing the Jewish communities countries invaded and occupied by Germany. Holocaust-related activities were located throughout those occupied territories, and included regions "liberated" from Russian hegemony, like the Baltics and Ukraine, whose indigenous populations collaborated with the Nazis in rounding-up their Jewish populations for extermination.
The Holocaust was largely comprised of a vast network of concentration camps that were built by the Germans in their own country as well as in Poland, site of the most infamous of all Nazi death camps, Auschwitz, as well as in Austria, and Ukraine. The Holocaust was, not, however, limited in scope to that network of concentration camps. The systemization and industrialization of the plan to exterminate the continent’s Jewish populations was preceded by less efficient actions that nevertheless succeeded in killing large numbers of Jews. Consequently, major Holocaust-related activities took place in areas where there were not concentration camps established. In such cases, most prominently, the September 1941 massacre at Babi Yar, a site near the Ukrainian capital Kiev, where an estimated 100,000 Jews were rounded up and methodically executed by gunshot, the German killing machine preceded the establishment of the network of camps that were a product of the more organized and industrialized plan to more efficiently rid Europe of its Jewish population.
Discussions of where, geographically, the Holocaust occurred are subject to debate because some countries, like France, that suffered German occupation, were not entirely innocent in their treatment of their Jewish communities. In fact, the fascist political movement known as Vichy France collaborated with the Germans in rounding up and deporting to German tens of thousands of French Jews and Jews who had fled to France from Germany. An estimated 75,000 such Jews were deported to concentration camps. Other countries were similarly complicit in collaborating with the Nazis, including Romania and Bulgaria, in addition to the aforementioned Polish and Baltic, especially Lithuanian, complicity.
A linkage to a map detailing the locations of German concentration camps is linked below.