The Balfour Declaration only gave a vague promise for a Jewish homeland in Palestine during WWI. The rationale behind it was quite murky. On one hand, one popular theory is that it was a ploy to win the support of Jewish Zionists within the Central Powers. Another contention is that the Balfour Declaration was an attempt to shore up world Jewish opinion towards the Entente. The ingrained antisemitism of the Foreign Office assumed that all Jew thought alike goes this theory.

In reality, the Balfour Declaration was something the British, with a few exceptions (like Orde Wingate), were somewhat embarrassed by in the interwar period. The influx of Zionists into the Palestinian Mandate created a unnecessary sectarian tension for the British governing body. The Balfour Declaration itself never explicitly said there was to be a Jewish state, but rather a Jewish "national home," which was an important semantic difference. The British mandate authorities tried to accomplish an unenviable task: to moderate the flow of Zionist refugees in a manner that would not upset Arab and Palestinian Jewish society. The British goal in the interwar period was clearly not an independent Jewish state.

Fast forward to the 1947, and the UN agrees upon a partition of the Palestinian Mandate and that is what creates the state of Israel.

Ironically, the Balfour Declaration itself had very little to do with the influx of Jewish emigration that led to the state of Israel. Zionism had only a moderate sway among Jews of Eastern and Central Europe. The Holocaust and the postwar antisemitism against refugees tended to remove the internal political obstacles to Zionism within many Jewish communities. Although one cannot say for sure, Israel and Zionist emigration would likely have still occurred had the Balfour Declaration never existed.

sources

Jacobson, Abigail. From Empire to Empire: Jerusalem between Ottoman and British Rule. Syracuse, N.Y.: Syracuse University Press, 2011.

Tomes, Jason. Balfour and Foreign Policy The International Thought of Conservative Statesman. Cambridge: Cambridge University Press, 2002.