1) Zionism and Palestinian nationalism both emerged in the late 19th/early 20th century in response to changing political and social forces in the Middle East and Europe. 2) The Balfour Declaration of 1917 expressed support for "the establishment in Palestine of a national home for the Jewish people" fueling tensions. 3) Conflict escalated in the 1920s-40s over immigration, land settlement and political control, culminating in open fighting after the 1947 UN partition plan and the establishment of Israel in 1948.