Wikipedia: Israel
On 14 May 1948, the day before the expiration of the British Mandate, the Jewish Agency proclaimed independence, naming the country Israel. The following day, the armies of four Arab countries —Egypt, Syria, Lebanon and Iraq – attacked Israel, launching the 1948 Arab–Israeli War; Saudi Arabia sent a military contingent to operate under Egyptian command; Yemen declared war but did not take military action. After a year of fighting, a ceasefire was declared and temporary borders, known as the Green Line, were established. Jordan annexed what became known as the West Bank and East Jerusalem, and Egypt took control of the Gaza Strip. The United Nations estimated that more than 700,000 Palestinians were expelled or fled from what would become Israel during the conflict.
Israel was accepted as a member of the United Nations by majority vote on 11 May 1949.