In the view of Christian Gerlach, Hitler announced his decision to annihilate the Jews on or around 12 December 1941, probably on 12 December during a speech to the Gauleiters, part of the Nazi Party leadership.[259] This was one day after the German declaration of war against the United States, which followed the Japanese attack on Pearl Harbour on 7 December and the United States declaration of war on Japan on 8 December.[260] According to Deborah Dwork and Robert Jan van Pelt, Hitler had trusted American Jews, whom he assumed were all-powerful, to keep their government out of the war in the interests of German Jews. When America declared war, the Jews were blamed.[261] Joseph Goebbels, the Reich Minister of Propaganda, noted of Hitler's speech: "He warned the Jews that if they were to cause another world war, it would lead to their destruction. ... Now the world war has come. The destruction of the Jews must be its necessary consequence."[260][o]
These programmes are best seen as a series of linked genocides, each having its own history, background, purpose and significance in the Nazi scheme of things. The Holocaust was the biggest of the killing programmes and, in certain important ways, different from the others. The Jews figured in Nazi ideology as the arch-enemy of the 'Aryan race', and were targeted not merely for terror and repression but for complete extinction. The Nazis failed in this aim because they ran out of time, but they pursued it fanatically until their defeat in 1945. The Holocaust led to widespread public awareness of genocide and to modern efforts to prevent it, such as the 1948 UN Convention on Genocide.
On March 23, 1933, the German Congress passed another important law, called the Enabling Act, which gave Hitler the power to rule by decree in case of an emergency. On that day, Germany still had a President and as Chancellor, Hitler was not yet the undisputed leader of Germany. The next day, on March 24, 1933, front page headlines in The Daily Express of London read "Judea Declares War on Germany - Jews of All the World Unite - Boycott of German Goods - Mass Demonstrations." The newspaper article mentioned that the boycott of German goods had already started.
Throughout the Middle Ages in Europe, Jews were subjected to antisemitism based on Christian theology, which blamed them for killing Jesus. Even after the Reformation, Catholicism and Lutheranism continued to persecute Jews, accusing them of blood libels and subjecting them to pogroms and expulsions.[60][61] The second half of the 19th century saw the emergence in the German empire and Austria-Hungary of the völkisch movement, which was developed by such thinkers as Houston Stewart Chamberlain and Paul de Lagarde. The movement embraced a pseudo-scientific racism that viewed Jews as a race whose members were locked in mortal combat with the Aryan race for world domination.[62] These ideas became commonplace throughout Germany,[63] with the professional classes adopting an ideology that did not see humans as racial equals with equal hereditary value.[64] Although the völkisch parties had support in elections at first, by 1914 they were no longer influential. This did not mean that antisemitism had disappeared; instead it was incorporated into the platforms of several mainstream political parties.[63]
There were no charges of killing prisoners in a gas chamber brought against the accused in the proceedings against the staff members of the Dachau camp, which were conducted by an American Military Tribunal at Dachau in November 1945, although a film of the gas chamber was shown at the Nuremberg International Military Tribunal on November 29, 1945, while the Dachau tribunal was in progress. This documentary film was taken by the Allies, under the direction of famed Hollywood director George Stevens; it showed the pipes through which the gas flowed into the gas chamber and the control wheels which regulated the flow of gas that came out of the shower heads.
Antisemitism, the new racist version of the old Jew-hatred, viewed the Jews as not simply a religious group but as members of a 'Semitic race', which strove to dominate its 'Aryan' rivals. Among the leading ideologues of this theory were a French aristocrat, the Comte Joseph de Gobineau, and an Englishman, Houston Stewart Chamberlain. Antisemitism proved a convenient glue for conspiracy theories - since Jews were involved in all sorts of ventures and political movements, they could be accused of manipulating all of them behind the scenes. Thus Jews were held responsible for Communism and capitalism, liberalism, socialism, moral decline, revolutions, wars, plagues and economic crises. As the Jews had once been demonised in medieval Europe, so the new antisemites (including many Christians) found new, secular ways of demonising them.

"During the Holocaust, Germans extinguished the lives of six million Jews and, had Germany not been defeated, would have annihilated millions more. The Holocaust was also the defining feature of German politics and political culture during the Nazi period, the most shocking event of the twentieth century, and the most difficult to understand in all of German history. The Germans' persecution of the Jews culminating in the Holocaust is thus the central feature of Germany during the Nazi period. It is so not because we are retrospectively shocked by the most shocking event of the century, but because of what it meant to Germans at the time and why so many of them contributed to it." Daniel Jonah Goldhagen, Hitler's Willing Executioners, Ordinary Germans and the Holocaust

In March 1944, part of the camp was redesignated as an Erholungslager ("recovery camp"),[11] where prisoners too sick to work were brought from other concentration camps. They were in Belsen supposedly to recover and then return to their original camps and resume work, but many of them died in Belsen of disease, starvation, exhaustion and lack of medical attention.[12]