WWI resulted in the British moving in, but it was still Palestine. The Brits had to contend with terrorists like Menachem Begin (I've seen his mugshot when the British caught him). After WWII, the Jews were given the land.

That's a somewhat inaccurate description of the history of the area.

There's always been a Jewish population in what would become the Mandate area - while most of the Jews were driven out during the Babylonian and Roman exiles, some remained. Jews began emigrating back to the area again in the 1880's, with the earliest waves of Aliyah, with the consent and approval of the various Sultans of the Ottoman Empire - and the area was the main objective of nationalist Zionist movements since that time. Roughly 10% of the population in the region was Jewish by the end of WWI.

The Brits ended up promising the Jews during WWI that a portion of the eventual Mandate area would be given to them, in an effort to get global (read American) Jewry to support the Allied Powers. Hence, the Balfour Declaration. However, the Brits (and the French) also promised territory in the area to various Arab leaders - and had carved it up amongst themselves in the secret Sykes-Picot Agreement - a set of contradictory promises that laid the groundwork for the century of conflict that followed.

The Ottoman Empire was carved up after its defeat in WWI, and the League of Nations gave Britain the Mandate over Palestine. Jewish migration to the area continued under the British Mandate Both the Jewish and Arab residents of the area came calling to the British to honor their promises. The Arabs revolted against the British from 1936-1939; then the Jews revolted against the British from 1944 until the end of the Mandate. There were large populations of both Arab and Jewish communities in the area by then.

The solution the UN came up with was the Partition of Palestine. Along the lines of the Partition of India, you would have an Arab state and a Jewish state. Of course, Egypt and Jordan immediately attacked in 1948, and seized nearly all of the land that would have been the Arab state for themselves....and most folks know the story from there.

But to coin a phrase, history did not begin in 1948.