Where did the holocaust take place; in what countries?

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.