In 1948, proceeding the 1947 United Nations Partition Plan that divided the area of Palestine into two states (see Resolution 181/Partition Plan), fighting increased between Palestinians and Jewish Zionists. Israel claimed independence as a state on May 14, which was followed by the entry of troops from Egypt, Syria, Lebanon, Iraq and Jordan (then known as Transjordan) into Palestine and subsequent fighting between these Arab troops and the new Israeli army. These events led up to the flight and expulsion of hundreds of thousands of Palestinians from the area that became the State of Israel. For details and sources see War of 1948, Al-Nakba and Israeli Independence Day.  http://www.justvision.org/glossary/1948