So after Ottoman empire ceased to exist when exactly did this happen? On which conference/by which treaty the power of disposition transfered in this way?
"The League of Nations decision to place Palestine under the administration of Great Britain as the Mandatory Power under the Mandates System adopted by the League. In principle, the Mandate was meant to be in the nature of a transitory phase until Palestine attained the status of a fully independent nation, a status provisionally recognized in the League’s Covenant, but in fact the Mandate’s historical evolution did not result in the emergence of Palestine as an independent nation.
The decision on the Mandate did not take into account the wishes of the people of Palestine, despite the Covenant’s requirements that “the wishes of these communities must be a principal consideration in the selection of the Mandatory”. This assumed special significance because, almost five years before receiving the mandate from the League of Nations, the British Government had given commitments to the Zionist Organization regarding the establishment of a Jewish national home in Palestine, for which Zionist leaders had pressed a claim of “historical connection” since their ancestors had lived in Palestine two thousand years earlier before dispersing in the “Diaspora”.
During the period of the Mandate, the Zionist Organization worked to secure the establishment of a Jewish national home in Palestine. The indigenous people of Palestine, whose forefathers had inhabited the land for virtually the two preceding millennia felt this design to be a violation of their natural and inalienable rights. They also viewed it as an infringement of assurances of independence given by the Allied Powers to Arab leaders in return for their support during the war. The result was mounting resistance to the Mandate by Palestinian Arabs, followed by resort to violence by the Jewish community as the Second World War drew to a close.
After a quarter of a century of the Mandate, Great Britain submitted what had become “the Palestine problem” to the United Nations on the ground that the Mandatory Power was faced with conflicting obligations that had proved irreconcilable. At this point, when the United Nations itself was hardly two years old, violence ravaged Palestine. After investigating various alternatives the United Nations proposed the partitioning of Palestine into two independent States, one Palestinian Arab and the other Jewish, with Jerusalem internationalized. The partition plan did not bring peace to Palestine, and the prevailing violence spread into a Middle East war halted only by United Nations action. One of the two States envisaged in the partition plan proclaimed its independence as Israel and, in a series of successive wars, its territorial control expanded to occupy all of Palestine. The Palestinian Arab State envisaged in the partition plan never appeared on the world’s map and, over the following 30 years, the Palestinian people have struggled for their lost rights"
Its not difficult to check the UN website.