The whole thing is a Myth.
Read "The Invention of the Jewish People" by Shlomo Sand (a Jewish history professor in Tel Aviv).
The modern-day Palestinians are the true descendants of the "Jews" who occupied the land centuries ago.
The modern-day "Jews" have no connection to the area...
Lloyd-George admitted in 1939 that the Balfour Declaration was a sop to American "Jews", who promised in return to get America into the First World War, on the British side (Britain was at risk of losing, according to L-G)