The standard Zionist position is that they showed up in Palestine in the late 19th century to reclaim their ancestral homeland. Jews bought land and started building up the Jewish community there. They were met with increasingly violent opposition from the Palestinian Arabs, presumably stemming from the Arabs' inherent anti-Semitism. The Zionists were then forced to defend themselves and, in one form or another, this same situation continues up to today.
The problem with this explanation is that it is simply not true, as the documentary evidence in this booklet will show. What really happened was that the Zionist movement, from the beginning, looked forward to a practically complete dispossession of the indigenous Arab population so that Israel could be a wholly Jewish state, or as much as was possible. Land bought by the Jewish National Fund was held in the name of the Jewish people and could never be sold or even leased back to Arabs (a situation which continues to the present).
The Arab community, as it became increasingly aware of the Zionists' intentions, strenuously opposed further Jewish immigration and land buying because it posed a real and imminent danger to the very existence of Arab society in Palestine. Because of this opposition, the entire Zionist project never could have been realized without the military backing of the British. The vast majority of the population of Palestine, by the way, had been Arabic since the seventh century A.D. (Over 1200 years)