Modern Zionism started at the end of the 19th century. Significant Immigration to Palestine had already started prior to the early 1930's. Certainly the events of WWII brought many refugees to Palestine but had WWIi never happened there would have been even a larger population of Jews available for immigration -and because they were treated so shabbily in Eastern Europe and the masses were so poor many would have immigrated.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: Epic Holocaust film 'Shoah' to be screened in Iran via satellite TV