The 1948 Palestine war was fought in the territory of what had been, at the start of the war, British-ruled Mandatory Palestine. It is known in Israel as the War of Independence (Hebrew: מלחמת העצמאות, Milkhemet Ha'Atzma'ut) and in Arabic as a central component of the Nakba (Arabic: النَّكْبَة, lit. 'the disaster'). It is the first war of the Israeli–Palestinian conflict and the broader Arab–Israeli conflict. During the war, the British terminated the Mandate and withdrew, ending a period of rule which began in 1917, during the First World War. Beforehand, the area had been part of the Ottoman Empire. In May 1948, the State of Israel was established by the Jewish Yishuv, its creation having been declared on the last day of the Mandate. During the war, around 700,000 Palestinian Arabs were displaced.

After the war, the former territory of the mandate was divided between the State of Israel, which captured about 78% of it, the Kingdom of Jordan (then known as Transjordan), which captured and later annexed the area that became the West Bank, and Egypt, which captured the Gaza Strip, a coastal territory on the shores of the Mediterranean Sea, in which the Arab League established the All-Palestine Government.

The war had two main phases, the first being the 1947–1948 civil war, which began on 30 November 1947,[19] a day after the United Nations voted to adopt the Partition Plan for Palestine, which divided the territory into Jewish and Arab sovereign states, and an international Jerusalem (UN Resolution 181). Partition was accepted by the Jewish leadership, but rejected by Palestinian Arab leaders and the Arab states.[20] This phase of the war is described by historians as the "civil", "ethnic" or "intercommunal" war, as it was fought mainly between Jewish and Palestinian Arab militias, supported by the Arab Liberation Army and the surrounding Arab states. Characterised by guerrilla warfare and terrorism, it escalated at the end of March 1948 when the Jews went on the offensive and concluded with their defeating the Palestinians in major campaigns and battles, establishing clear frontlines. During this period the British still maintained a declining rule over Palestine and occasionally intervened in the violence.

The British terminated the Mandate at midnight at the end of 14 May 1948. On that day, the last remaining British troops and personnel departed the city of Haifa and the Jewish leadership in Palestine declared the establishment of the State of Israel. This was followed the next day by the invasion of Palestine by the surrounding Arab armies and expeditionary forces.

The invasion marked the beginning of the second phase of the war, the 1948 Arab–Israeli War. The Egyptians advanced on the southern coastal strip and were halted near Ashdod; the Jordanian Arab Legion and Iraqi forces captured the central highlands of Palestine. Syria and Lebanon fought several skirmishes with the Israeli forces in the north. The Jewish militias, organised into the Israel Defense Forces, managed to halt the Arab forces. The following months saw fierce fighting between the IDF and the Arab armies, which were being slowly pushed back. The Jordanian and Iraqi armies managed to maintain control over most of the central highlands of Palestine and capture East Jerusalem, including the Old City. Egypt's occupation zone was limited to the Gaza Strip and a small pocket surrounded by Israeli forces at Al-Faluja. In October and December 1948, Israeli forces crossed into Lebanese territory and pushed into Egypt's Sinai Peninsula, encircling the Egyptian forces near Gaza City. The last military activity happened in March 1949, when Israeli forces captured the Negev desert and reached the Red Sea. In 1949, Israel signed separate armistices with Egypt on 24 February, Lebanon on 23 March, Transjordan on 3 April, and Syria on 20 July. During this period the flight and expulsion of the Palestinian Arabs continued.