What is Zionism, and how is it an example of nationalism?

It started out as a form of defensive nationalism for the persecuted Jews. The aim was to create a homeland for the Jews. After the war it changed to a form of militant fascism as the Zionists resorted to terroristic bombings and killings to seize land they had little ancestral claim to and (from the 70s onwards) inflicted on the Palestinians the same atrocites they suffered in the early years of the Nazi regime (ghettos, chemical weapons, deliberate killing of women and children)