After Israel declared its independence on May 14, 1948, the fighting intensified with other Arab forces joining the Palestinian Arabs in attacking territory in the former Palestinian mandate. On the eve of May 14, the Arabs launched an air attack on Tel Aviv, which the Israelis resisted. This action was followed by the invasion of the former Palestinian mandate by Arab armies from Lebanon, Syria, Iraq, and Egypt. Saudi Arabia sent a formation that fought under the Egyptian command. British trained forces from Transjordan eventually intervened in the conflict, but only in areas that had been designated as part of the Arab state under the United Nations Partition Plan and the corpus separatum of Jerusalem. After tense early fighting, Israeli forces, now under joint command, were able to gain the offensive.
Though the United Nations brokered two cease-fires during the conflict, fighting continued into 1949. Israel and the Arab states did not reach any formal armistice agreements until February. Under separate agreements between Israel and the neighboring states of Egypt, Lebanon, Transjordan, and Syria, these bordering nations agreed to formal armistice lines. Israel gained some territory formerly granted to Palestinian Arabs under the United Nations resolution in 1947. Egypt and Jordan retained control over the Gaza Strip and the West Bank respectively. These armistice lines held until 1967. The United States did not become directly involved with the armistice negotiations, but hoped that instability in the Middle East would not interfere with the international balance of power between the Soviet Union and the United States.