Jewish immigration to the Land of Israel increased despite British bans, and the Haganah, Etzel (Irgun), Lehi, and Palmach groups where formed in "Palestine" as defensive forces by the Jews against increasing Arab attacks.

The leaders of the Zionist Congress continued to wrestle with the United Nations for a resolution establishing a Jewish state in "Palestine." A partition plan was put forth by the UN on November 29, 1947 leaving the Jews with a much reduced portion of "Palestine" while giving a large chuck of the territory for an Arab state (see map of 1947 UN Partition Plan). Reluctantly, the Jewish leadership accepted the plan, however, the Arabs rejected it, claiming all of "Palestine" for their own and rejecting the establishment of any Jewish, Zionist entity in the Middle East.

On December 11, 1947, the British government, in light of the recent UN partition plan for "Palestine", announced its intention to terminate its mandatory control of "Palestine" on May 15, 1948. On May 14, 1948, as the last British soldiers left "Palestine", long time Zionist leader David Ben Gurion declared the independence of the State of Israel. It was almost exactly 50 years since Theodor Herzl had proclaimed at the First Zionist Congress in Basel, Switzerland that in 50 years the world would realize the establishment of the Jewish state.

The declaration of the State of Israel by Ben Gurion was immediately followed by the invasion of 6 Arab armies, those of Egypt, Syria, Lebanon, Jordan, as well as contingents from Iraq and Saudi Arabia. The Israel Defense Forces were formed as a result of the combining of all former Jewish defense organizations during the war, and the tiny, reborn Jewish nation fought for her life. The fighting ended one year later when, in the spring of 1949, Israel signed UN brokered armistice agreements with Egypt, Syria, Lebanon, and Jordan. Israel was left in control of a greater area than had been allotted by the UN partition plan. (See War of Independence)

Following the War of Independence Jewish immigrants from Arab nations began arriving en masse. Well over half a million Jewish residents of Arab lands immigrated to Israel from 1948 to 1952 as a result of greatly increased anti-Jewish sentiment in those nations.

In 1950, the Israeli government established the Law of Return giving all Jews worldwide the unquestioned right to immigrate to and become a part of the State of Israel. Zionism had realized its greatest goal, the reestablishment of Israel as a nation on her ancient soil. However, in the coming years it would be no less important for Zionism to remain a unifying force among the Jews as it was during the decades of hardship in Europe. Zionism now shifted from being a vehicle to reestablish the Jewish state to being the force behind the growth and prosperity of that state.