“Before the declaration of Israel as a state in May 1948, the apron of land surrounding Gaza contained dozens of Palestinian Arab towns and villages, the largest of which was al-Majdal—what is now the entirely Jewish city of Ashkelon.
When, on Nov. 29, 1947, the United Nations General Assembly voted to divide Palestine into a Jewish state and a Palestinian Arab state, this whole area—including Gaza, its surrounding areas, and parts of the Negev Desert—was designated to be included within the Arab state. But the U.N. failed to provide money, troops, or administrators to implement its decision. Abandoning Palestine to chaos, the British, who had ruled the territory for more than 20 years, pulled their forces out of city after city, region after region. As they did so, Jews and Arabs plunged into an atrocity-filled civil war over which areas would fall under Jewish or Arab rule.
The result of this civil war, of battles between Israel and the expeditionary forces of Arab states that invaded Palestine in May 1948, and of increasingly systematic Israeli campaigns to expel Arab civilians from territories that were to have been the Arab state, was the displacement of 750,000 Palestinians; 200,000 of them found shelter in a narrow wedge of coastal Palestine occupied by Egyptian troops—what became known as the Gaza Strip. Israel’s refusal to allow those who fled or were expelled to return to their homes, and its subsequent destruction of their villages, towns, and neighborhoods, turned these displaced persons into refugees.”
https://www.yahoo.com/news/gaza-became-open-air-prison-165951249.html