The land began to develop again only with the start of the Jewish settlements after the establishment of the Zionist movement, initiating waves of Jewish immigration to the Holy Land.
Significant development came only after the conquest of the land by the British Empire in 1917. This period is when many Arabs from neighboring countries made their way into the Land of Israel as migrant workers.
A mandate to rule the Land of Israel—the British Mandate for Palestine, from the ancient Roman name—was given to the British (among other areas) by the League of Nations, the organization that preceded the UN. A mandate was given for a limited time, with the aim of preparing the local people for eventual independence and self-rule. With the Mandate for Palestine, Britain officially reiterated all its commitments from the 1917 Balfour Declaration to a national home for the Jewish people in the Land of Israel.
The Mandate for Palestine's founding document explicitly stated that a national home for the Jewish people would be established in its territory. It did not expressly mention a national home for any other people.
The Mandate documented the deep historical connection between the Jewish people and the Land of Israel, from biblical times to the present day. The territory designated for the British Mandate of Palestine included Transjordan (today, the Hashemite Kingdom of Jordan), Israel, Gaza, and Judea and Samaria (i.e., the West Bank).
The charter of the British Mandate for Palestine has been ratified by the British Parliament, the U.S.
Congress, and the League of Nations. When the UN was established, it ratified all the Mandates of the League of Nations, including the British Mandate for Palestine. The Mandate, therefore, is a binding international treaty which has become part of international law, British law, and American law.
In the 1967 Six-Day War, Egypt, Syria, and Jordan tried again to destroy Israel. The State of Israel won the war and took the Golan Heights, Judea and Samaria (West Bank), the Sinai Peninsula, and the Gaza strip. All the territory occupied in the war (except for the Sinai) belongs to the Jewish people according to international law, in accordance with the Treaty of San Remo and the British Mandate for Palestine. Israel returned the whole of Sinai to Egypt in the peace treaty of 1979, and unilaterally pulled out of Gaza in 2005.