2005 as International Holocaust Remembrance Day. In the decades after the war, survivors such as Primo Levi, Viktor Frankl, and Elie Wiesel wrote memoirs of their experiences, and the camp became a dominant symbol of the Holocaust. In 1947, Poland founded the Auschwitz-Birkenau State Museum on the site of Auschwitz I and II, and in 1979 it was named a World Heritage Site by UNESCO. Background The ideology of National Socialism (Nazism) combined elements of "racial hygiene", eugenics, antisemitism, pan-Germanism, and territorial expansionism, Richard J. Evans writes. Adolf Hitler and his Nazi Party became obsessed by the "Jewish question". Both during and immediately after the Nazi seizure of power in Germany in 1933, acts of violence against German Jews became ubiquitous, and legislation was passed excluding them from certain professions, including the civil service and the law. Harassment and economic pressure encouraged Jews to leave Germany; their businesses were denied access to markets, forbidden from advertising in newspapers, and deprived of government contracts. On 15 September 1935, the Reichstag passed the Nuremberg Laws. One, the Reich Citizenship Law, defined as citizens those of "German or related blood who demonstrate by their behaviour that they are willing and suitable to serve the German People and Reich faithfully", and the Law for the Protection of German Blood and German Honor prohibited marriage and extramarital relations between those with "German or related blood" and Jews. When Germany invaded Poland in September 1939, triggering World War II, Hitler ordered that the Polish leadership and intelligentsia be destroyed. The area around Auschwitz was annexed to the German Reich, as part of first Gau Silesia and from 1941 Gau Upper Silesia. The camp at Auschwitz was established in April 1940, at first as a quarantine camp for Polish political prisoners. On 22 June 1941, in an attempt to obtain new territory, Hitler invaded the Soviet Union. The first gassing at Auschwitz—of a group of Soviet prisoners of war—took place around August 1941. By the end of that year, during what most historians regard as the first phase of the Holocaust, 500,000–800,000 Soviet Jews had been murdered in mass shootings by a combination of German Einsatzgruppen, ordinary German soldiers, and local collaborators. At the Wannsee Conference in Berlin on 20 January 1942, Reinhard Heydrich outlined the Final Solution to the Jewish Question to senior Nazis, and from early 1942 freight trains delivered Jews from all over occupied