According to a PBS Special Documentary Film called 'Six Days in June', during May 1967, Egyptian Vice President Anwar El Sadat headed a delegation to the Soviet Union, where Soviet Official in charge of the Middle East Viktor Simeonov passed onto him intelligence information stating that the Israelis had amassed an invasion force of 12 brigades on the Syrian border and were preparing to attack Syria in a week's time. There is controversy about whether this information was correct or not, but it definitely helped push Syria and Egypt towards war with Israel. Sadat delivers the Soviets intelligence information to Nasser, who was assured by the Head of the Armed Forces Marshall Abdul Hakim Amer that their forces were able to fight back any Israeli attack and win.

On May 16, 1967, the commander of the United Nations' Emergency Force (UNEF), General Indar Jit Rikhye, was handed a letter from General Muhammad Fawzy, Chief of Staff of the United Arab Republic , requesting that he issue orders to withdraw all of the UNEF troops immediately. The UN Secretary-General U Thant suggested that UNEF be relocated onto the Israeli side of the border, but Israel refused, and on May 19, 1967, the UNEF commander was given the order to withdraw.

Union between Syria and Egypt, this lasted from 1958 until 1961. Although the two countries separated in September 1961, the name, United Arab Republic, was still used until 1971 to refer to Egypt. 31

Closure of Straits of Tiran
On May 22, 1967, Egypt closed the Straits of Tiran [see map] to all Israeli shipping and all ships headed to Eilat. This blockade cut off Israel's only supply route with Asia and stopped the flow of oil from its main supplier, Iran.

The straits were open for Israel only after the Israeli, French and British attack on Egypt in 1956 in what is known as the 'Canal War' or 'Suez War'. Israel claimed that the United States had given it assurances after the Canal War, that it recognized the Jewish State's right of access to the Straits of Tiran; however, the Straits were inside the territorial waters of Egypt. Egypt and Israel were enemies, and no state would allow its enemies to pass through its territory.32, 33

Furthermore, pressure was put on Nasser accusing him of allowing Israeli shipment through the straits. Nasser was facing a strategic decision, for closing the straits might ignite a war, and keeping it open for Israeli shipment could have been seen as a sign of weakness on the part of Egypt.  
Still, US President Johnson stated that the blockade was illegal and he unsuccessfully tried to organize an international flotilla to test it. After the war, on June 19, 1967, he determined the closure of the Straits of Tiran to be the casus belli.

Egypt-Jordan Treaty

The Egyptian President Jamal Abdel Nasser and King Husain of Jordan were not on good terms until a few days before the war. At that period of time, during Nasser's command, Jordan was under a lot of pressure to convert into a republic. King Husain was in a dilemma, for if he did not join the war, he would be considered a traitor, especially when he failed to defend Es-Sumu' against the Israeli attack, a failure that could cost him the throne. In addition, after watching the neighboring Arab countries join their forces, he believed in Israel's defeat, and wanted to have his share of the trophy.
On May 30, 1967, King Husain flew to Cairo where he signed a mutual defense treaty with Nasser; thereby confirming that Jordan had joined the military alliance already in place between Egypt and Syria.
The Jordanian forces were given to the command of an Egyptian General Abdul Munim Riad. At the same time several other Arab states not bordering Israel, including Iraq, Sudan, Kuwait and Algeria, stated that they would mobilize their armed forces if a war was to start.

Line-up for War

The Egyptians were not planning on going to war with Israel, for they had large numbers of forces, including three of their best battalions, tied down in Yemen backing the anti-Saudi, anti-royalist forces there. Moreover, U Thant came to Cairo on the May 23, 1967, and took a promise from Nasser not to start a war, and he later reported that to Abba Eban. However, Nasser placed two divisions in the Sinai desert as a sign of ally support, showing that were the Israelis to attack Syria, they would attack them in return.

On May 15, 1967, the divisions were placed in Sinai; however, 12 hours into mobilizing the troops, Nasser found out that the soviets information about the Israeli attack was not correct. In later years Rabin was quoted in 'Le Monde', on February 29, 1968, as saying, "I do not think Nasser wanted war. The two divisions he sent to the Sinai in May [1967] would not have been sufficient to launch an offensive against Israel. He knew it and we knew it." 35

On August 8, 1982, Israeli Prime Minister Menachem Begin made a speech saying, "In June, 1967, we again had a choice. The Egyptian army concentrations in the Sinai did not prove that Nasser was really about to attack us. We must be honest with ourselves. We decided to attack him". 36

According to the PBS documentary 'Six Days in June', Nasser could have back off from war, but he did not dare dampen the excitement he created throughout the Arab World, for the sent off of the troops was broadcast on radio and T.V. all over the Middle East, and had created excitement amongst the Arab population. Nonetheless, in one of his speeches, Nasser said that "if the Jews want war, we say 'welcome we are ready'". However, when asked in an interview about his statement "if Israel attacks, she will be completely destroyed", his reply was: "if somebody attacks you what would be your reaction? If somebody attacks us we will react. React, in war, means destruction." The reporter then asked him: "if Israel does not attack, will you leave them alone?" He answered: "Yes we'll leave them alone. We have no intention to attack Israel."

On the Israeli side, the matter was almost settled. The Israeli forces had more or less completed mobilizing by the end of May, and the army was in favor of starting a war at once. However, Eshkol hesitated,37and the Cabinet had not yet given the O.K. to go to war.

On May 22, 1967, David Ben Gurion, then an Israeli Cabinet Member and retired Prime Minister, had a meeting with the cabinet, where he advised Eshkol not to launch a war without the support of the super-powers. Furthermore, Ben Gurion thought that the crisis with Egypt was a result of Eshkol's unbalanced actions, such as attacking Es-Sumu' and provoking Syria in the Demilitarized Zone. He also scolded Rabin for his actions in mobilizing the reserves, saying "You have brought the state to a most dangerous situation, and you are to be blamed for it". 38Later, Rabin had a nervous break down incapacitating him for forty-eight hours during May 22-24, 1967.

However, some of the Israeli generals, including Ariel Sharon, were insisting on launching a war without delay. Ariel Sharon proposed to Yitzhak Rabin on the eve of the war to start the fight without the Cabinet's approval.39 After so much pressure, Levi Eshkol caved in and on June 2, 1967, set up a national unity government, and appointed General Moshe Dayan, who was favored by the IDF commanders, as Defense Minister. Ironically, Eshkol and Nasser were put into similar situations.
According to the PBS documentary 'Six Days in June', Eshkol was accused of being incapable and ineffectual as to lead the Israeli forces, especially after his stumbling and stuttering during a radio speech on May 28, 1967. The public wanted action, and the generals insisted on striking the Egyptians first. As for Nasser, the same pressure was put upon him by his generals who too insisted on going to war with Israel. As UNEF General Indar Jit Rikhye states in the documentary film, Nasser was afraid that if he did not go along with the army's demands, a coup might take place, and he might be assassinated.

As for the combatant armies, many historians gave different accounts for their number. However, the estimated numbers and descriptions in various resources show that they were ill-matched. Although the armies of the Arab countries, united, outnumbered the Israeli army, the Israelis were better trained, better equipped, and had the advantage of striking first.