The (in)famous 1917 Balfour Declaration to Baron Rothschild on Palestine (as it was then called) perfectly encapsulates the root of the conflict: a colonial power pledging to European Jews land that belonged to neither.

Zionists naturally accepted the '47 UN partition plan as it gave them a state they didn't have; the Arabs of Palestine naturally rejected it as it took part of their existing homeland. 

It was a tactical acceptance, as David Ben-Gurion (who would become Israel's first prime minister) candidly articulate a decade before: "We shall accept a state with fixed boundaries today, but the boundaries of Zionist aspiration are the concern of the Jewish people and no external factors can limit them."