May 14, 1948, United Nations Resolution 181 went into effect, creating the sovereign nation of Israel from the former British Mandate of Palestine. The following day, five Arab neighbors invaded. Israel defended itself, losing only the Gaza Strip to Egypt and the West Bank of the Jordan River, including the 'old city' of Jerusalem, to Jordan. For the next 19 years, Israel faced hundreds of deadly conflicts with its neighbors over its own right to exist, its increasing military power, and the status of non-Jewish residents and refugees.
Throughout this time frame, the United States was concerned about increasing Soviet power and influence in the Arab states and began arming Israel. Meanwhile, many of the Arab nations were bickering among themselves. Egyptian leader Gamal Nasser asserted his intentions to unify the Arab nations, but Saudi Arabia and Jordan resisted his efforts to gain control. Syria criticized Egypt for its lack of leadership against Israel.
But in a May 1967 speech, Nasser defended himself, claiming, 'We were waiting for the day when we would be fully prepared and confident of being able to adopt strong measures if we were to enter the battle with Israel… Recently we felt we are strong enough, that if we were to enter a battle with Israel, with God's help, we could triumph… The battle will be a general one and our basic objective will be to destroy Israel.'
Abruptly, Nasser expelled UN peacekeepers that had been stationed in the Sinai since the Suez Crisis, and then moved tens of thousands of men, tanks, and artillery to his border with Israel the following day. Three days later, on May 22, he blockaded all ships bound for Israel through the Straits of Tiran. Now, a decade earlier, U.S. President Eisenhower had promised that the United States would treat another closure of the Straits of Tiran as an act of war. But while President Johnson did condemn the illegal blockade in 1967, he failed to generate international help in ending it.
Nasser's boldness made him a hero. There were celebrations in the streets throughout the Arab world, and nations that had been at each other's throats were suddenly unified in their single purpose of destroying Israel. Over the next ten days, nearly a quarter million Arab troops marched toward Israel. Oil-producing nations agreed to boycott any nation that defended Israel. The U.S. warned Israel to wait.