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The Palestinian people (Arabic: الشعب الفلسطيني‎, ash-sha‘b al-Filasṭīnī), aka Palestinians (Arabic: الفلسطينيون‎, al-Filasṭīniyyūn; Hebrew: פָלַסְטִינִים&lrm or Palestinian Arabs (Arabic: الفلسطينيين العرب‎, al-Filasṭīniyyīn al-ʿarab), are an ethnonational group. Roughly half of all Palestinians reside in historic Palestine, the area encompassing the West Bank, the Gaza Strip, and Israel. [en.m.wikipedia.org]
The 1948 exodus was a central component of the fracturing, dispossession and displacement of Palestinian society, known as the Nakba (Arabic: النكبة‎, al-Nakbah, literally "disaster", "catastrophe", or "cataclysm" ) [en.m.wikipedia.org]

The 1948 (or First) Arab–Israeli War was the second and final stage of the 1947–1949 Palestine war. It formally began following the end of the British Mandate for Palestine at midnight on 14 May 1948; the Israeli Declaration of Independence had been issued earlier that day, and a military coalition of Arab states entered the territory of British Palestine in the morning of 15 May.
It formally began following the end of the British Mandate for Palestine at midnight on 14 May 1948; the Israeli Declaration of Independence had been issued earlier that day, and a military coalition of Arab states entered the territory of British Palestine in the morning of 15 May.
The first deaths of the 1947–1949 Palestine war occurred on 30 November, 1947 during an ambush of two buses carrying Jews. There had been tension and conflict between the Arabs and the Jews, and between each of them and the British forces since the 1917 Balfour Declaration and the 1920 creation of the British Mandate of Palestine. British policies dissatisfied both Arabs and Jews. Arab opposition developed into the 1936–1939 Arab revolt in Palestine, while the Jewish resistance developed into the 1944–1947 Jewish insurgency in Palestine. In 1947, these ongoing tensions erupted into civil war following the 29 November 1947 adoption of the United Nations Partition Plan for Palestine. [en.m.wikipedia.org]

Sykes–Picot Agreement. Complicating the issue was the Balfour Declaration of 1917, promising British support for a Jewish "national home" in Palestine.
[en.m.wikipedia.org]

The partitioning of the Ottoman Empire after the war led to the domination of the Middle East by Western powers such as Britain and France, and saw the creation of the modern Arab world and the Republic of Turkey. [en.m.wikipedia.org]

The Balfour Declaration was a public statement issued by the British government in 1917 during the First World War announcing support for the establishment of a "national home for the Jewish people" in Palestine, then an Ottoman region with a small minority Jewish population. The declaration was contained in a letter dated 2 November 1917 from the United Kingdom's Foreign Secretary Arthur Balfour to Lord Rothschild, a leader of the British Jewish community, for transmission to the Zionist Federation of Great Britain and Ireland.
It sought the support of Zionist ambitions in order to enlist the support of Jews in the wider war. Further drafts were discussed by the British Cabinet during September and October, with input from Zionist and anti-Zionist Jews but with no representation from the local population in Palestine. [en.m.wikipedia.org]

Israel (/ˈɪzriəl, ˈɪzreɪəl/; Hebrew: יִשְׂרָאֵל‎ Yisra'el; Arabic: إِسْرَائِيل&lrm, officially known as the State of Israel (Hebrew: מְדִינַת יִשְׂרָאֵל‎, Medinat Yisra'el), is a country in Western Asia. Canaanite tribes are archaeologically attested since the Middle Bronze Age, while the Kingdoms of Israel and Judah emerged during the Iron Age. The land was controlled as a mandate of the British Empire from 1920 to 1948 when Israel was recognized by the U.N. [en.m.wikipedia.org]

The Israeli Declaration of Independence, formally the Declaration of the Establishment of the State of Israel (Hebrew: הכרזה על הקמת מדינת ישראל&lrm, was proclaimed on 14 May 1948 (5 Iyar 5708) by David Ben-Gurion, the Executive Head of the World Zionist Organization, Chairman of the Jewish Agency for Palestine, and soon to be first Prime Minister of Israel. It declared the establishment of a Jewish state in Eretz-Israel, to be known as the State of Israel, which would come into effect on termination of the British Mandate at midnight of that day. [en.m.wikipedia.org]