One of the most essential elements of the Zionist project revolves around a clear and accurate definition of the Jewish identity.  This definition has been quite hard to pin down due to two main factors.  The first is the relationship between the Jewish diaspora, the Jewish community living outside of Israel, and the Jews living inside Israel.  The second is whether or not the Jewish identity should be based on an ethnic, national or religious definition related to Judaism.  The difficult part is that Zionist literature views the existence of a Jewish diaspora as contradictory to the concept of Zionism as a whole, which hinges on the return of the Messiah.  In order for the Messiah to return, all separated Jews from across the world must return to these Israeli territories. One of the most prominent explanation for the Zionist project is what happened in the nineteenth century for Jews in Europe, the Holocaust massacre at the hands of Nazism and the emergence of the term anti-Semitism.