Six Day War Battle Front in West Bank: Jordan was reluctant to enter the war. Nasser used the obscurity of the first hours of the conflict to convince Hussein that he was victorious; he claimed as evidence a radar sighting of a squadron of Israeli aircraft returning from bombing raids in Egypt which he said was an Egyptian aircraft en route to attacking Israel. One of the Jordanian brigades stationed in the West Bank was sent to the Hebron area in order to link with the Egyptians. Hussein decided to attack.

Prior to the war, Jordanian forces included 11 brigades totaling some 55,000 troops, equipped with some 300 modern Western tanks. Of these, nine brigades (45,000 troops, 270 tanks, 200 artillery pieces) were deployed in the West Bank, including elite armored 40th, and 2 in the Jordan Valley. The Arab Legion was a long-term-service, professional army relatively well-equipped and well-trained. Furthermore, Israeli post-war briefings said that the Jordanian staff acted professionally as well, but was always left "half a step" behind by the Israeli moves. The tiny Royal Jordanian Air Force consisted of only 24 UK Hawker Hunter fighters. According to the Israelis, the British-made Hawker Hunter was essentially on par with the French-built Dassault Mirage III - the IAF's best plane.

Against Jordan's forces on the West Bank, Israel deployed about 40,000 troops and 200 tanks (8 brigades). Israeli Central Command forces consisted of five brigades. The first two were permanently stationed near Jerusalem and were called the Jerusalem Brigade and the mechanized Harel Brigade. Mordechai Gur's 55th paratrooper brigade was summoned from the Sinai front. An armored brigade was allocated from the General Staff reserve and advanced toward Ramallah, capturing Latrun in the process. The 10th armored brigade was stationed north of the West Bank Region. The Israeli Northern Command provided a division (3 brigades) led by Maj. Gen. Elad Peled, which was stationed to the north of the West Bank, in the Jezreel Valley.

The IDF's strategic plan was to remain on the defensive along the Jordanian front, to enable focus in the expected campaign against Egypt. However, on the morning of 5 June, Jordan began shelling targets in west Jerusalem, Netanya, and the outskirts of Tel Aviv. The Royal Jordanian Air Force attacked Israeli airfields. Despite this, both air and artillery attacks caused little damage, and Israel sent a message promising not to initiate any action against Jordan if it stayed out of the war. Hussein replied that it was too late, "the die was cast". On the evening of June 5, the Israeli cabinet convened to decide what to do; Yigal Allon and Menahem Begin argued that this was an opportunity to take the Old City of Jerusalem, but Eshkol decided to defer any decision until Moshe Dayan and Yitzhak Rabin could be consulted. Uzi Narkis made a number of proposals for military action, including the capture of Latrun, but the cabinet turned him down. The Israeli military only commenced action after Jordanian forces made thrusts in the area of Jerusalem.

Jordanian troops seized the Government House compound, used as the headquarters for the UN observers in a Demilitarized zone since the 1949 Armistice Agreements. In addition, the Jordanians opened a heavy-artillery barrage on western Jerusalem, as well as targeting the center of the country.

At the UN Security Council meeting of June 5, 1967 Secretary-General U Thant reported that:

"at 1330 hours local time today approximately one company of Jordanian soldiers occupied the garden of the Government House.

"General Bull later informed me by an emergency message that Jordanian troops had not with-drawn and were demanding to enter Government House itself and had demanded that no telephone calls be made from Government House. Firing was continuing and mortar shells were now landing within the Government House compound. United Nations Headquarters lost radio contact with UNTSO headquarters in Jerusalem at 0852 hours New York time, at which time Jordanian troops occupied Government House1/. This also means that United Nations Headquarters has lost direct contact with headquarters UNEF, whose messages are routed through UNTSO."

1/ it is to be noted that the report that Jordanian troops had "occupied" Government House was originally based on incomplete information owing to a communicaitons [sic] breakdown caused by the events in the Government House area. On the basis of a review of events and a checking with the Chief of Staff of UNTSO, it was later determined that the actual facts as regards the reported entry of Jordanian troops into Government House on 5 June 1967 were as follows: at approximately 1445 hours local time, three Jordanian soldiers entered Government House over the protest of UNTSO, but were persuaded by UNTSO staff to leave the building after about ten minutes.

On June 6, Israeli units were scrambled to attack Jordanian forces in the West Bank. In the afternoon of that same day, Israeli Air Force (IAF) strikes destroyed the Royal Jordanian Air Force. By the evening of that day, the Jerusalem infantry brigade moved south of Jerusalem, while the mechanized Harel and Gur's paratroopers encircled it from the north. The reserve paratroop brigade completed the Jerusalem encirclement in the bloody Battle of Ammunition Hill, in which 71 Jordanian and 37 Israeli soldiers were killed. Fearing damage to holy places and having to fight in built-up areas, Dayan ordered his troops not to go into the city itself.

On June 7, heavy fighting ensued. The infantry brigade attacked the fortress at Latrun, capturing it at daybreak, and advanced through Beit Horon towards Ramallah. The Harel brigade continued its push to the mountainous area of northwest Jerusalem, linking the Mount Scopus campus of Hebrew University with the city of Jerusalem. By the evening, the brigade arrived in Ramallah. The IAF detected and destroyed the 60th Jordanian Brigade en route from Jericho to reinforce Jerusalem.

In the north, one battalion from Peled's division was sent to check Jordanian defenses in the Jordan Valley. A brigade belonging to Peled's division captured the western part of the West Bank, another captured Jenin and the third (equipped with light French AMX-13s) engaged Jordanian M48 Patton main battle tanks to the east.

Dayan had ordered his troops not to enter Jerusalem; however, upon hearing that the UN was about to declare a ceasefire, he changed his mind, and without cabinet clearance, decided to take the city. Gur's paratroopers entered the Old City of Jerusalem via the Lion's Gate, and captured the Western Wall and the Temple Mount. The intense battle for the Old City was fought mostly by paratroopers, who had to engage in heavy street fighting. The Israeli high command had ordered the IDF not to use heavy armor in the Old City - since this was an area holy to Judaism, the Israeli government wanted to leave it intact. The Jerusalem brigade then reinforced the paratroops, and continued to the south, capturing Judea, Gush Etzion and Hebron. The Harel brigade proceeded eastward, descending to the Jordan River.

In the West Bank, one of Peled's brigades seized Nablus; then it joined one of Central Command's armored brigades to fight the Jordanian forces; as the Jordanians held the advantage of superior equipment and were equal in numbers to the Israelis.

Again, the air superiority of the IAF proved paramount as it immobilized the enemy, leading to its defeat. One of Peled's brigades joined with its Central Command counterparts coming from Ramallah, and the remaining two blocked the Jordan river crossings together with the Central Command's 10th (the latter crossed the Jordan river into the East Bank to provide cover for Israeli combat engineers while they blew the Abdullah and Hussein bridges, but was quickly pulled back because of American pressure).

No specific decision had been made to capture any other territories controlled by Jordan. After the Old City was captured, Dayan told his troops to dig in to hold it. When an armored brigade commander entered the West Bank on his own initiative, and stated that he could see Jericho, Dayan ordered him back. It was only after intelligence reports indicated that Hussein had withdrawn his forces across the Jordan River that Dayan ordered his troops to capture the West Bank. According to Narkis:

First, the Israeli government had no intention of capturing the West Bank. On the contrary, it was opposed to it. Second, there was not any provocation on the part of the IDF. Third, the rein was only loosened when a real threat to Jerusalem's security emerged. This is truly how things happened on June 5, although it is difficult to believe. The end result was something that no one had planned.

Six Day War Battle Front in Gaza Strip and Sinai Peninsula: The Egyptian forces consisted of seven divisions: four armored, two infantry, and one mechanized infantry. Overall, Egypt had around 100,000 troops and 900-950 tanks in the Sinai, backed by 1,100 APCs and 1,000 artillery pieces. This arrangement was thought to be based on the Soviet doctrine, where mobile armor units at strategic depth provide a dynamic defense while infantry units engage in defensive battles.

Israeli forces concentrated on the border with Egypt included six armored brigades, one infantry brigade, one mechanized infantry brigade, three paratrooper brigades, giving a total of around 70,000 men and 700 tanks, who were organized in three armored divisions. The Israeli plan was to surprise the Egyptian forces in both timing (the attack exactly coinciding with the IAF strike on Egyptian airfields), location (attacking via northern and central Sinai routes, as opposed to the Egyptian expectations of a repeat of the 1956 war, when the IDF attacked via the central and southern routes) and method (using a combined-force flanking approach, rather than direct tank assaults).

The northernmost Israeli division, consisting of three brigades and commanded by Major General Israel Tal, one of Israel's most prominent armor commanders, advanced slowly through the Gaza Strip and El-Arish, which were not heavily protected.

The central division (Maj. Gen. Avraham Yoffe) and the southern division (Maj. Gen. Ariel Sharon), however, entered the heavily defended Abu-Ageila-Kusseima region, leading to what is known as the Battle of Abu-Ageila. Egyptian forces there included one infantry division (the 2nd), a battalion of tank destroyers and a tank regiment, formed of Soviet WW2 armor, which included 90 T-34-85 tanks (with 85 mm guns), 22 SU-100 tank destroyers (with 100 mm guns), and about 16,000 men, while the Israelis had a man-power of about 14,000, and 150 post-WW2 tanks including the AMX-13 with 90 mm guns, Centurions, and M50 Super Shermans.

Sharon initiated an attack, precisely planned, coordinated and carried out. He sent two of his brigades to the north of Um-Katef, the first one to break through the defenses at Abu-Ageila to the south, and the second to block the road to El-Arish and to encircle Abu-Ageila from the east. At the same time, a paratrooper force was heliborne to the rear of the defensive positions and attacked the Egyptian artillery positions. Although the paratrooper force's plan quickly fell apart, the confusion sown among the artillery crews helped to slow but not quite stop artillery fire. Combined forces of armor, paratroopers, infantry, artillery, and combat engineers then attacked the Egyptian position from the front, flanks and rear, cutting the enemy off. The breakthrough battles, which were in sandy areas and minefields, continued for three and a half days until Abu-Ageila fell. About 4,000 Egyptian soldiers were killed, and losses in military hardware were heavy, including 40 tanks. The Israelis lost 33 men and 19 tanks.

At the same time, Israeli forces attacked El Arish and Jebel Libni, Bir Gafgafa, and Gaza areas, capturing the cities as well as a number of fortified towns. They met fierce resistance, but they continued their rapid advance. As well as numerous armored battles which saw Israeli armor defeat numerically superior Egyptian armor, many Egyptian tanks were also knocked out by Israeli infantry carrying anti-tank weapons. The fiercest fighting was at Gaza, where the Israelis fought for two days and suffered heavy casualties before capturing it. An independent Israeli armored brigade also captured an Egyptian outpost at Kunitla. During the ground fighting, remnants of the Egyptian Air Force attacked Israeli ground troops, but took heavy losses from the Israeli Air Force and anti-aircraft units.

Many of the Egyptian units remained intact and could have tried to prevent the Israelis from reaching the Suez Canal or engaged in combat in the attempt to reach the canal. However, when the Egyptian Minister of Defense, Field Marshal Abdel Hakim Amer heard about the fall of Abu-Ageila, he panicked and ordered all units in the Sinai to retreat. This order effectively meant the defeat of Egypt.

As Egyptian columns retreated, Israeli aircraft attacked them, using napalm bombs. The attacks destroyed hundreds of vehicles and caused heavy casualties. Due to the Egyptians' retreat, the Israeli High Command decided not to pursue the Egyptian units but rather to bypass and destroy them in the mountainous passes of West Sinai. Therefore, in the following two days (June 6 and 7), all three Israeli divisions (Sharon and Tal were reinforced by an armored brigade each) rushed westwards and reached the passes. Sharon's division first went southward then westward to Mitla Pass with air support. It was joined there by parts of Yoffe's division, while its other units blocked the Gidi Pass. These passes became killing grounds for the retreating Egyptians as a result. Tal's units stopped at various points to the length of the Suez Canal.

The Israeli Navy landed six combat divers to infiltrate Alexandria harbor. The divers sank an Egyptian minesweeper before being taken prisoner.

Israel's blocking action was partially successful. Only the Gidi pass was captured before the Egyptians approached it, but at other places, Egyptian units managed to pass through and cross the canal to safety. Due to the haste of the Egyptian retreat, soldiers often abandoned weapons or military equipment, as well as hundreds of vehicles. Many Egyptian soldiers were cut off from their units had to walk about 200 kilometers through by foot before reaching the Suez Canal with limited supplies of food and water and were exposed to intense heat. Thousands of soldiers died as a result. Many Egyptian soldiers chose instead to surrender to the Israelis.

On June 8, Israel had completed the capture of the Sinai by sending infantry units to Ras-Sudar on the western coast of the peninsula. Sharm El-Sheikh, at its southern tip, had already been taken a day earlier by units of the Israeli Navy.

In Summary: Several tactical elements made the swift Israeli advance possible: first, the surprise attack that quickly gave the Israeli Air Force complete air superiority over its Egyptian counterpart; second, the determined implementation of an innovative battle plan; third, the lack of coordination among Egyptian troops. These factors would prove to be decisive elements on Israel's other fronts as well.

Six Day War Fighting Front, Israel Preliminary Air Attack: Israel's first and most critical move was a surprise attack on the Egyptian Air Force. Egypt had by far the largest and the most modern of all the Arab air forces, consisting of about 420 combat aircraft, all of them Soviet-built and with a heavy quota of top-of-the line MiG-21 capable of attaining Mach 2 speed. Initially, both Egypt and Israel announced that they had been attacked by the other country.

Of particular concern to the Israelis were the 30 Tu-16 “Badger” medium bombers, capable of inflicting heavy damage on Israeli military and civilian centers. On June 5 at 7:45 Israeli time, as civil defense sirens sounded all over Israel, the Israeli Air Force (IAF) launched Operation Focus (Moked). All but 12 of its nearly 200 operational jets left the skies of Israel in a mass attack against Egypt's airfields. The Egyptian defensive infrastructure was extremely poor, and no airfields were yet equipped with hardened aircraft shelters capable of protecting Egypt's warplanes. Most of the Israeli warplanes headed out over the Mediterranean Sea before turning toward Egypt. Others flew over the Red Sea. Meanwhile, the Egyptians hindered their own defense by effectively shutting down their entire air defense system: they were worried that rebel Egyptian forces would shoot down the plane carrying Field Marshal Amer and Lt-Gen. Sidqi Mahmoud, who were en route from al Maza to Bir Tamada in the Sinai to meet the commanders of the troops stationed there. In any event, it did not make a great deal of difference as the Israeli pilots came in below Egyptian radar cover and well below the lowest point at which its SA-2 surface-to-air missile batteries could bring down an aircraft. Although the powerful Jordanian radar facility at Ajlun observed the waves of Israeli aircraft and reported the code word for "war" up the Egyptian command chain, Egyptian command and communications problems prevented the warning from reaching the targeted airfields. The Israelis employed a mixed attack strategy: bombing and strafing runs against planes parked on the ground, themselves, and bombing the runways with tarmac-shredding penetration bombs to disable them and leave survivng aircrtaft unable to take off. These aircraft were later taken out by several more attack waves. The operation was more successful than expected, catching the Egyptians by surprise and destroying virtually all of the Egyptian Air Force on the ground, with few Israeli losses. Over 300 Egyptian aircraft were destroyed and 100 pilots were killed, although the number of aircraft actually lost by the Egyptians is disputed. Among the Egyptian planes lost were all 30 Tu-16 bombers, as well as 27 out of 40 Il-28 bombers, 12 Su-7 fighter-bombers, over 90 MiG-21s, 20 MiG-19s, 25 MiG-17 fighters and around 32 assorted transport planes and helicopters. The Israelis lost 19 planes, including two destroyed in air-to-air combat and 13 downed by anti-aircraft artillery. The attack guaranteed Israeli air superiority for the rest of the war.

Following the success of the initial attack waves against the major Egyptian airfields and subsequent air raids, attacks were carried out that afternoon against Israel by the Jordanian, Syrian, and Iraqi air forces. Subsequent attacks against Egyptian, Jordanian, Syrian, and Iraqi fields destroyed most of their air forces. By the evening of the first day, the Jordanian air force was wiped out, losing over 20 Hawker Hunter fighters, as well as six transport aircraft and two helicopters. The Syrian Air Force lost some 32 MiG 21s, and 23 MiG-15 and MiG-17 fighters, and two Ilyushin Il-28 bombers, two-thirds of its fighting strength. A number of Iraqi Air Force aircraft were destroyed at H3 base in western Iraq by an Israeli airstrike which included 12 out of 20 MiG-21s, two MiG-17s, five Hunter F6s, and three Il-28 bombers. A lone Iraqi Tu-16 bomber was shot down earlier that day by Israeli anti-aircraft fire while attempting to bomb Tel Aviv. On the morning of June 6, 1967, a Lebanese Hunter, one of 12 Lebanon had, was shot down over the Lebanon/Israel border by an Israeli Mirage IIICJ piloted by Uri Even-Nir.

By nightfall, Israel said it destroyed 416 Arab aircraft, while losing 26 of their own in the first two days of the war. Israeli aircraft shot down included six out of 72 of its Mirage IIICJ fighters, four out of its 24 Super Mystère fighters, eight out of 60 Mystère IVA ground attack aircraft, four out of 40 Ouragan ground attack aircraft, and five out of 25 of its Vautour II medium bombers. Twelve Israeli pilots were killed, five wounded, and four captured. The numbers of Arab aircraft claimed destroyed by Israel were at first regarded as "greatly exaggerated" by the Western press. However, the fact that the Egyptian, Jordanian, and other Arab air forces made practically no appearance for the remaining days of the conflict proved that the numbers were most likely authentic. Throughout the war, Israeli aircraft continued strafing Arab airfield runways to prevent their return to usability. Meanwhile, Egyptian state-run radio had reported an Egyptian victory, falsely claiming that 70 Israeli planes had been downed on the first day of fighting.

Six Day War: Israeli Preparations for War, Before the war, Israeli pilots and ground crews had trained extensively in rapid refitting of aircraft returning from sorties, enabling a single aircraft to sortie up to four times a day (as opposed to the norm in Arab air forces of one or two sorties per day). This enabled the IAF to send several attack waves against Egyptian airfields on the first day of the war, overwhelming the Egyptian Air Force, and also allowed it to knock out other Arab air forces on the same day. This also has contributed to the Arab belief that the IAF was helped by foreign air forces (see below). Pilots were also extensively schooled about their targets, and were forced to memorize every single detail. They also rehearsed the attack numerous times on dummy runways.

The Egyptians had constructed fortified defenses in the Sinai. These designs were based on the assumption that an attack would come from the few roads leading through the desert, rather than the difficult desert terrain. The Israelis chose not to risk attacking the Egyptian defenses head-on, and instead to surprise them from an unexpected direction. They had practiced driving vehicles through sof dunes in the Negev, and discovered that vehicles would get greater maneuverability in desert terrain if tires were partially deflated. As a result, they could choose their angle of attack, and advance through areas the Egyptians least expected. In order to keep the performance of Israeli soldiers high in the heat of the Sinai desert, the Israeli army ordered that soldiers be supplied with one liter of water every hour, rather than the previous one liter per day. As a result, soldiers were able to perform better than their Egyptian counterparts.

In order to strike the Golan Heights, the Mossad (Israeli secret service) had sent agent Eli Cohen to infiltrate the Syrian government, where he exploited his high-ranking position to provide crucial intelligence. Feigning sympathy for Syrian soldiers, he ordered trees planted by every Syrian emplacement to shade them. These trees were later used as targeting markers by the Israelis. Intelligence had also revealed where the most difficult terrain was, so a route of attack was chosen that would both avoid natural tank traps and surprise the Syrians. In order to successfully storm the Syrian bunkers, the Israelis utilized the Uzi submachine gun, which was more suitable for close combat than the AK-47, the standard weapon of the Syrian Army.

The Israeli army had a total strength, including reservists, of 264,000, though this number could not be sustained, as the reservists were vital to civilian life. James Reston, writing in the New York Times on May 23, 1967, noted, "In discipline, training, morale, equipment and general competence his [Nasser's] army and the other Arab forces, without the direct assistance of the Soviet Union, are no match for the Israelis... Even with 50,000 troops and the best of his generals and air force in Yemen, he has not been able to work his way in that small and primitive country, and even his effort to help the Congo rebels was a flop."

On the evening of June 1, Israeli Minister of Defense Moshe Dayan called Chief of Staff Yitzhak Rabin and the GOC, Southern Command Brigadier General Yeshayahu Gavish to present plans against Egypt. Rabin had formulated a plan in which Southern Command would fight its way to the Gaza Strip and then hold the territory and its people hostage until Egypt agreed to reopen the Straits of Tiran; while Gavish had a more comprehensive plan that called for the destruction of Egyptian forces in the Sinai. Rabin favored Gavish's plan, which was then endorsed by Dayan with the caution that a simultaneous offensive against Syria should be avoided.

On the eve of the war, Egypt massed approximately 100,000 of its 160,000 troops in the Sinai, including all of its seven divisions (four infantry, two armored and one mechanized), as well as four independent infantry and four independent armored brigades. No less than a third of them were veterans of Egypt's intervention into the Yemen Civil War and another third were reservists. These forces had 950 tanks, 1,100 APCs and more than 1,000 artillery pieces. At the same time some Egyptian troops (15,000 - 20,000) were still fighting in Yemen. Nasser's ambivalence about his goals and objectives was reflected in his orders to the military. The general staff changed the operational plan four times in May 1967, each change requiring the redeployment of troops, with the inevitable toll on both men and vehicles. Towards the end of May, Nasser finally forbade the general staff from proceeding with the Qahir ("Victory") plan, which called for a light infantry screen in the forward fortifications with the bulk of the forces held back to conduct a massive counterattack against the main Israeli advance when identified, and ordered a forward defense of the Sinai. In the meantime, he continued to take actions intended to increase the level of mobilization of Egypt, Syria and Jordan, in order to bring pressure on Israel.

Syria's army had a total strength of 75,000 and amassed them along the Syrian border. Jordan's army had 55,000 troops, including 300 tanks along the Jordanian border, 250 of which were US M48 Patton, sizable amounts of M113 APCs, a new battalion of mechanized infantry, and a paratrooper battalion trained in the new US-built school. They also had 12 battalions of artillery and six batteries of 81 mm and 120 mm mortars.

Documents captured by the Israelis from various Jordanian command posts record orders from the end of May for the Hashemite Brigade to capture Ramot Burj Bir Mai'in in a night raid, codenamed "Operation Khaled". The aim was to establish a bridgehead together with positions in Latrun for an armored capture of Lod and Ramle. The "go" codeword was Sa'ek and end was Nasser. The Jordanians also planned for the capture of Motza and Sha'alvim in the strategic Jerusalem Corridor. Motza was tasked to Infantry Brigade 27 camped near Ma'ale Adummim: "The reserve brigade will commence a nighttime infiltration onto Motza, will destroy it to the foundation, and won't leave a remnant or refugee from among its 800 residents".

100 Iraqi tanks and an infantry division were readied near the Jordanian border. Two squadrons of fighter-aircraft, Hawker Hunters and MiG 21 respectively, were rebased adjacent to the Jordanian border.

On June 2, Jordan called up all reserve officers, and the West Bank commander met with community leaders in Ramallah to request assistance and cooperation for his troops during the war, assuring them that "in 3 days we'll be in Tel-Aviv".

The Arab air forces themselves were aided by volunteer pilots from the Pakistan Air Force acting in independent capacity, as well as some aircraft from Libya, Algeria, Morocco, Kuwait, and Saudi Arabia to make up for the massive losses suffered on the first day of the war.

The Israeli cabinet met on May 23 and decided to launch an attack if the Straits of Tiran were not re-opened by May 25. Following an approach from United States Under Secretary of State for Political Affairs Eugene Rostow to allow time for the negotiation of a nonviolent solution, Israel agreed to a delay of ten days to two weeks. UN Secretary General, U Thant, visited Cairo for mediation and recommended a moratorium in the Straits of Tiran and a renewed diplomatic effort to solve the crisis. Egypt agreed, but Israel rejected these proposals. Nasser's concessions did not necessarily suggest that he was making a concerted effort to avoid war. The decision benefited him both politically and strategically. Agreeing to diplomacy helped garner international political support. Moreover, every delay gave Egypt time to complete its own military preparations and coordinate with the other Arab forces. Also, Israel's rejection did not necessarily demonstrate a desire for war so much as it demonstrated the urgency it felt the situation warranted. Israel felt it could not afford to sustain total mobilization for long. Caught up in Arab enthusiasm for military action and encouraged by the lack of response to the closure of the Straits, Egyptian Field Marshal Amer planned for initiating an attack on Israel in late May. He told one of his generals that "This time we will be the ones to start the war." This was counter to Nasser's strategy of pushing Israel to start the war. Historian Michael Oren states that Egyptian sources are divided over why Nasser did not veto Amer's plan. Oren suggests that "Nasser was apprised of [the plan] but lacked the political strength to override Amer's order. Also, the preparation of an Egyptian invasion of Israel had certain advantages for Nasser"

The U.S. also tried to mediate, and Nasser agreed to send his vice-president to Washington to explore a diplomatic settlement. Most American diplomats who worked in the Middle East were sympathetic to Nasser's views on the Straits, with several of them arguing that the U.S. should ignore both its on-the-record promises to Israel regarding the Straits being open and international law; a few diplomats who were not as impressed by threats from Arab nations advised the Johnson Administration to back the flotilla option as a "show of force" that would forestall war from breaking out. The meeting did not happen because Israel launched its offensive. Some analysts suggest that Nasser took actions aimed at reaping political gains, which he knew carried a high risk of precipitating military hostilities. On this view, Nasser's willingness to take such risks was based on his fundamental underestimation of Israel's capacity for independent and effective military action.

On May 25, 1967, Israeli Foreign Minister Abba Eban landed in Washington “with instructions to discuss American plans to re-open the Strait of Tiran”. As soon as he arrived, he was given new instructions in a cable from the Israeli government. The cable said that Israel had learned of an imminent Egyptian attack, which overshadowed the blockade. No longer was he to emphasize the strait issue; he was instructed to ‘inform the highest authorities of this new threat and to request an official statement from the United States that an attack on Israel would be viewed as an attack on the United States.”According to most sources, including those involved, the new instructions were sent at the instigation of Chief of Staff Yitzhak Rabin, who was eager to force an American decision – either Johnson would have to commit to specific American action then, or Israel would be free to act on its own. Historian Michael Oren explains Eban's reaction to the new instructions: "Eban was livid. Unconvinced that Nasser was either determined or even able to attack, he now saw Israelis inflating the Egyptian threat - and flaunting their weakness - in order to extract a pledge that the President, Congress-bound, could never make." He described the cable as an ' act of momentous irresponsibility... eccentric...' which 'lacked wisdom, veracity and tactical understanding,' and later came to the conclusion that the genesis of the cable was Rabin's indecisive state of mind.

Despite his own skepticism, Eban followed his instructions during his first meeting with Secretary Rusk, Under Secretary Rostow, and Assistant Secretary Lucius Battle. American intelligence experts spent the night analyzing each of the Israeli claims. On May 26, Eban met with United States Secretary of State Dean Rusk, Defense Secretary Robert McNamara, and finally with President Lyndon B. Johnson. In a memo to the President, Rusk rejected the claim of an Egyptian and Syrian attack being imminent, plainly stating "our intelligence does not confirm the Israeli estimate". According to declassified documents from the Johnson Presidential Library, President Johnson and other top officials in the administration did not believe war between Israel and its neighbors was necessary or inevitable. "All of our intelligence people are unanimous that if the UAR attacks, you will whip hell out of them", Johnson told Eban during a visit to the White House on May 26. This assertion was made in accordance with a CIA assessment that Israel could “defend successfully against simultaneous Arab attacks on all fronts or hold on any three fronts while mounting successfully a major offensive on the fourth." Consequently, Johnson declined to airlift special military supplies to Israel or even to publicly support it. Eban left the White House distraught.

In a lecture given in 2002, Oren said, "Johnson sat around with his advisors and said, ‘What if their intelligence sources are better than ours?’ Johnson decided to fire off a Hotline message to his counterpart in the Kremlin, Alexei Kosygin, in which he said, ‘We've heard from the Israelis, but we can't corroborate it, that your proxies in the Middle East, the Egyptians, plan to launch an attack against Israel in the next 48 hours. If you don't want to start a global crisis, prevent them from doing that.’ At 2:30 a.m. on May 27, Soviet Ambassador to Egypt Dimitri Pojidaev knocked on Nasser's door and read him a personal letter from Kosygin in which he said, ‘We don't want Egypt to be blamed for starting a war in the Middle East. If you launch that attack, we cannot support you.’ Amer consulted his sources in the Kremlin, and they corroborated the substance of Kosygin's message. Despondent, Amer told the commander of Egypt's air force, Major General Mahmud Sidqi, that the operation was cancelled." According to then Egyptian Vice-President Hussein el-Shafei, as soon as Nasser knew what Amer planned, he cancelled the operation.

On 30 May, Nasser responded to Johnson's request of 11 days earlier and agreed to send his Vice President, Zakkariya Muhieddin, to Washington on June 7 to explore a diplomatic settlement in "precisely the opening the White House had sought". Historian Michael Oren writes that Rusk was "mad as hell" and that Johnson later wrote "I have never concealed my regret that Israel decided to move when it did".

Within Israel's political leadership, it was decided that if the US would not act, and if the UN could not act, then Israel would have to act. On 1 June, Moshe Dayan was made Israeli Defense Minister, and on June 3 the Johnson administration gave an ambiguous statement; Israel continued to prepare for war. Israel's attack against Egypt on June 5 began what would later be dubbed the Six-Day War. According to Martin van Creveld, the IDF pressed for war: "...the concept of 'defensible borders' was not even part of the IDFs own vocabulary. Anyone who will look for it in the military literature of the time will do so in vain. Instead, Israel's commanders based their thought on the 1948 war and, especially, their 1956 triumph over the Egyptians in which, from then Chief of Staff Dayan down, they had gained their spurs. When the 1967 crisis broke they felt certain of their ability to win a 'decisive, quick and elegant' victory, as one of their number, General Haim Bar Lev, put it, and pressed the government to start the war as soon as possible". Some of Israel's political leaders, however, hoped for a diplomatic solution.