It has its roots in religion - in the assertion that the Jews murdered Jesus.
The most notorious anti-Semitic practices in the 19thc were the 'pogroms ' in Russia.
It also stems from cultural differences - by culture, by religion, by rituals and dress.
In the 19thc Jews became prominent in the professions and active in industry and commerce - this often led to envy and criticism.
At the same time, Jews became increasingly associated with liberalism, radicalism, socialism and communism - the idea took root in anti-Semitic circles that to do away with Jews would also do away with capitalism and socialism.
The Nazis and race theory:
Central to Nazi thinking was the belief in the superiority of the Aryans - the white Europeans of the blond, Nordic type. It was argued that assimilation of Jews would result in a tainting of Aryan stock through racial mixing of blood. Social Darwinism transferred Darwin 's idea of the 'survival of the fittest ' to the human world. The 'master race ' would become the Volkgemeinschaft, and the inferior and weak would become victims. The theory of eugenics (which argued that society should discourage 'unfit ' members from breeding) was also influential. Mein Kampf developed Hitler 's ideas. He blamed the Jews for Germany 's troubles, claimed they were responsible for the invention of Marxism, for Germany 's defeat in WWI and for the subsequent humiliation of Versailles.
The historical debate:
Did Hitler plan the Holocaust from the moment the Nazis took power? There has been an important debate on this subject. On the one hand there are those who believe that it was the Nazis’ constant and unwavering intention to destroy European Jewry; these historians are called the intentionalists. On the other side there are those that argue that the Holocaust was reached by a 'twisted road ' and that many forces within the German state as well as without helped to bring it about.