Causes and Course of the War

Setting the Stage: A Regional Crisis in Slow Motion

To understand why the Six-Day War broke out in June 1967, it is important to see that it did not come out of nowhere. It followed almost two decades of unresolved issues after the 1948 war, repeated border clashes, and a regional competition for leadership in the Arab world.

After 1949, Israel and several neighboring states had armistice agreements but no peace treaties. The borders were not fully accepted, and each side accused the other of violations. Palestinian refugees were living mainly in neighboring Arab states and in the Gaza Strip and West Bank, with no political solution in sight. Within this already tense situation, a series of specific developments in the mid 1960s created a sense of looming confrontation.

The war in 1967 was preceded by a period in which both sides believed that the strategic balance was shifting. Israel felt increasingly encircled and alarmed by rhetoric from Arab leaders and by Soviet military support for its neighbors. Arab governments, especially Egypt and Syria, felt pressure to demonstrate firmness and leadership over the Palestinian question and over the broader Arab struggle against Israel. These pressures mixed with misperceptions and miscalculations to create a crisis that no one fully controlled.

Immediate Causes: Tensions Along Borders

One central cause of the war was chronic tension along Israel’s borders, especially with Syria, and the way these clashes escalated in the years just before 1967.

Israel and Syria disputed control over demilitarized zones along their armistice line and over water resources. The Jordan River and its tributaries were vital for agriculture and settlement, and both sides developed plans to divert or control water flows. Skirmishes over land use, plowing fields, and cultivation sometimes turned into artillery duels.

From the early 1960s, Palestinian guerrilla groups carried out attacks on Israel from neighboring territories. Fatah, which became the leading faction in the Palestine Liberation Organization, launched operations mainly from Syrian and Jordanian territory. These actions included sabotage of infrastructure and cross-border ambushes. Israel usually responded with large military reprisals against the states from which the attacks originated. These operations were designed to deter further attacks, but in practice they often raised tension with Arab governments and increased pressure on them not to appear weak.

The Syrian government, which at the time had a radical, pan-Arab orientation, allowed and supported some of these guerrilla activities. Israel saw this as proof that Syria was a central threat, and clashes between the Israeli and Syrian armies intensified. Air battles occurred, including one where Israeli aircraft shot down several Syrian planes. Each incident fed a cycle of rhetorical escalation and mutual fear.

The Egyptian Role and Closing of the Straits

The key steps that directly preceded the war involved Egypt under President Gamal Abdel Nasser. Nasser was a central Arab figure who presented himself as a leader of Arab nationalism and a champion of the Palestinian cause. His actions in May and early June 1967 were understood by Israel as signs of an approaching war, while Nasser believed they would deter Israel and enhance his position in the Arab world.

The crisis began in earnest when the Soviet Union told Egypt that Israel was massing troops on the Syrian border, suggesting an impending attack on Syria. The accuracy of this report is disputed, and evidence suggests that the Israeli buildup was not as the Soviets described. However, Nasser treated the information as serious, both because he relied on Soviet support and because he was under pressure to demonstrate solidarity with Syria.

In mid May 1967, Nasser ordered Egyptian forces into the Sinai Peninsula, near the Israeli border. This move reversed a more limited Egyptian military posture in the area that had existed since the 1956 Suez Crisis. At the same time, Nasser requested the withdrawal of the United Nations Emergency Force, which had been stationed in parts of Sinai and the Gaza Strip after 1956 to reduce the risk of direct Egyptian Israeli clashes. The UN secretary general complied and removed the peacekeeping force. From Israel’s perspective, this removal took away a key buffer and increased the risk of surprise attack.

The most dramatic step came when Nasser announced, in late May, that Egypt would close the Straits of Tiran to Israeli shipping. These narrow waterways connect the Red Sea to the Israeli port of Eilat and are crucial for access to certain trade routes. Israel had repeatedly declared that closure of the Straits would be seen as a casus belli, that is, a just cause for war. Many states outside the region, including the United States, also considered freedom of navigation an important principle. The closure of the Straits of Tiran signaled that the crisis had moved into a new and dangerous phase.

Alliance Signals, Mobilization, and Escalating Rhetoric

While these developments unfolded, Egypt received political and military backing from other Arab governments. Although there were rivalries within the Arab world, the crisis created pressure to show unity against Israel.

Jordan’s King Hussein, who had previously had a tense relationship with Nasser, signed a defense pact with Egypt on the eve of war. Iraqi forces moved toward Jordanian territory to support this front. Syria was already allied with Egypt, and their military coordination increased. These public arrangements created, at least on paper, a multi front alignment that heightened Israel’s sense of encirclement.

Arab radio broadcasts and speeches by some leaders contained highly militant language and references to previous wars. In Israel, such statements were widely heard and interpreted as announcements of a coming attempt to destroy the state. Within Arab societies, much of the rhetoric reflected both genuine hostility and political competition over who was more committed to the Palestinian cause.

Mobilization followed rhetoric. Arab states placed their forces on higher alert. Israel also mobilized reserves, a step that had major economic and social costs in a small state that depended heavily on citizen soldiers. The presence of large numbers of Israeli reservists in uniform, combined with news of Egyptian and Syrian deployments, created a sense among Israeli leaders and the public that war might be imminent and possibly existential.

Participation and signaling by outside powers added to the uncertainty. The Soviet Union supplied weapons to several Arab states and had an interest in demonstrating support for its partners. The United States and some European countries had ties with Israel and with certain Arab governments and tried to manage the crisis diplomatically. However, there was no clear and enforceable international mechanism to reverse the closure of the Straits, restore UN forces, or reliably deter either side from initiating hostilities.

The Decision for Preemptive War

In late May and early June 1967, Israel’s leadership debated possible responses. Israeli officials perceived that the Egyptian moves in Sinai, the removal of UN forces, the blockade of the Straits, and the regional alliances represented a convergence of threats that could eventually limit Israel’s strategic options or even invite coordinated attack.

Some Israeli leaders believed that delay would allow Arab forces to strengthen their positions, bring in more advanced weapons, and force Israel into a weaker diplomatic posture. Others worried about international opinion if Israel fired the first shot. The United States, in particular, urged restraint and explored the possibility of an international maritime operation to reopen the Straits, but no swift solution materialized.

Within Israel, fear of a repeat of 1948, this time under more dangerous military conditions, influenced the thinking of both the political and military leadership. Based on intelligence assessments of Arab deployments and air capabilities, Israeli planners concluded that a rapid and decisive first strike could neutralize enemy air forces before they took off and thereby protect Israeli cities and forces from attack.

In early June, after days of tension and partial mobilization, the Israeli government gave its air force the order to strike. The war that followed is often described as preemptive from the Israeli perspective. From the Arab perspective, the war was seen differently and the question of who bears primary responsibility for escalation remains a subject of debate, but the sequence of actions is clear: the decisive opening move in direct combat came from the Israeli side.

Day One: The Airstrike That Shaped the War

The Six-Day War began on the morning of June 5, 1967. The opening operation was a large-scale Israeli air attack targeting Egyptian air bases. Israeli planes flew low to avoid radar detection, using carefully planned routes and timing designed to catch Egyptian aircraft on the ground.

The results of the first wave of attacks were devastating for the Egyptian air force. Many aircraft were destroyed on their runways. Follow up sorties targeted remaining airfields and infrastructure. Within hours, Egypt’s air capabilities were severely reduced. This initial success gave Israel what its planners had sought, control of the skies over the emerging battlefield.

Once the attack on Egypt was underway, Israeli aircraft also struck airfields in Jordan and Syria to prevent their air forces from posing a serious threat. As news of the attacks spread, Arab leaders announced that they were under Israeli assault and presented the conflict as an Israeli aggression. In Israel, the public learned that the long-feared war had begun, but also that the opening moves appeared to be militarily favorable.

On the ground, fighting between Egyptian and Israeli forces in Sinai began almost immediately after the air strikes, as Israeli armored and infantry units advanced toward Egyptian positions. At the same time, Jordanian artillery shelled Israeli areas in and around Jerusalem and other parts of Israel, and Israeli forces responded along that front as well.

Sinai and the Egyptian Front

Once air superiority was secured over Sinai, the Israeli military advanced rapidly against Egyptian ground forces. Before the war, Egypt had moved large formations into Sinai, but these units faced difficulties with logistics, communication, and coordination. The loss of air cover made it even harder for them to maneuver and organize an effective defense.

Israeli operations in Sinai followed several axes, pushing toward key road junctions, passes, and strongpoints. Intense battles took place at fortified positions and along important routes. As the scale of the air attacks became clear, confusion spread in parts of the Egyptian command structure. Conflicting orders and poor communication contributed to a breakdown of organized resistance in some areas.

By June 6 and 7, Egyptian units were retreating westward toward the Suez Canal. In the course of this withdrawal, many vehicles were abandoned or destroyed, and Egyptian casualties mounted. Israeli forces continued to advance to secure the peninsula. Within a few days, Israel had gained control over most of Sinai up to the eastern bank of the Suez Canal, transforming its strategic depth on the southern front.

The Jordanian Front and the West Bank

While the Sinai fighting unfolded, hostilities on the Jordanian front escalated quickly. Jordanian artillery and forces, coordinated with Egypt through the defense pact, opened fire on Israeli positions and targets, including in West Jerusalem. The Jordanian army took positions in and around the Old City and along key ridges overlooking Israeli populated areas.

Israel responded with air strikes against Jordanian air bases, which reduced Jordan’s ability to operate its air force. On the ground, Israeli units advanced into the West Bank. Urban and rural fighting occurred in several locations, including around East Jerusalem, which had been under Jordanian control since 1948.

A central operation took place in and around Jerusalem itself. Israeli forces engaged Jordanian troops in neighborhoods and at strategic points that controlled access to the Old City. After intense combat, including battles for key high ground, Israeli units moved into the Old City through the Lion’s Gate on June 7. Jordanian forces withdrew across the Jordan River.

By the time a ceasefire was accepted on this front, Israel had taken control of the West Bank, including East Jerusalem. This outcome fundamentally changed the map of the conflict and brought many important religious and historical sites under direct Israeli control, a development that would have long term political and symbolic consequences.

The Syrian Front and the Golan Heights

On the northern front with Syria, heavy artillery exchanges had already occurred in the months before June 1967, and they continued as the war began. Syrian forces shelled Israeli communities in the Galilee from positions in the Golan Heights, which provided a steep and strategically advantageous plateau overlooking northern Israel.

During the first days of the war, Israel focused primarily on the Egyptian and Jordanian fronts. Only later did Israeli decision makers turn their attention fully to the Syrian theater. Once they decided to act, Israeli forces launched a ground offensive against well entrenched Syrian positions on the Golan Heights.

The terrain made this a difficult and costly operation. Syrian defenses included bunkers, trenches, and artillery that covered narrow approaches up the slopes. Israeli units advanced in coordinated assaults, supported by air power that targeted Syrian artillery and logistical lines. After intense fighting over several days, Israeli troops captured key positions and eventually took control of most of the Golan Heights by June 10.

The capture of the Golan Heights removed, at least in the short term, the immediate threat of Syrian artillery fire on northern Israeli communities. It also created a new front line that was closer to Damascus and that would become a major point of contention in later negotiations and conflicts.

Diplomatic Moves and Ceasefire

While the fighting unfolded, diplomatic activity took place at the United Nations and in various capitals. The rapid pace of Israeli military success surprised many observers. Arab governments called for international intervention to halt the attacks, while Israel emphasized that it was acting in self-defense in response to an existential threat and a blockade of its shipping.

The UN Security Council convened and began to discuss draft resolutions calling for a ceasefire. The United States and the Soviet Union, despite being on opposite sides of the broader Cold War, both had reasons to prevent a prolonged conflict that could escalate or draw them more directly into confrontation.

Ceasefires were agreed in stages, corresponding to each front. Egypt accepted a ceasefire after losing control of Sinai. Jordan complied after losing the West Bank and East Jerusalem. Syria held out longer, but after the loss of major positions on the Golan Heights and mounting international pressure, it too agreed to halt fighting. By June 11, 1967, formal ceasefires were in place and large-scale combat operations had stopped.

The war had lasted six days from the opening airstrike to the final ceasefire, which is why it is commonly known as the Six-Day War. In that short time, the territorial realities of the conflict had been dramatically altered, setting the stage for new phases of diplomacy, occupation, and resistance that would follow.

Military Outcomes and the New Map

By the end of the war, Israel had gained control of three main areas that had previously been held by neighboring Arab states. From Egypt, Israel captured the Sinai Peninsula and the Gaza Strip. From Jordan, Israel captured the West Bank, including East Jerusalem. From Syria, Israel captured the Golan Heights.

These territorial changes gave Israel improved strategic depth compared with the pre war armistice lines, particularly in the south and north. At the same time, Israel now governed large populations of Palestinians in the West Bank and Gaza Strip who did not hold Israeli citizenship and had their own national aspirations. How to administer and decide the future of these territories became one of the central challenges of the next decades.

Casualties and material losses were uneven. Arab states suffered heavy losses in personnel, equipment, and infrastructure. Israel also sustained casualties and losses but emerged with a clear military victory and a strengthened sense of its own capabilities. However, this victory carried with it the burden of controlling new territories and populations, and raised new questions in international law and diplomacy that would soon appear at the United Nations and in broader global debates.

Perceptions, Myths, and Unanswered Questions

The causes and course of the Six-Day War are not remembered in the same way by all parties. In Israeli narratives, the war is often recalled as a necessary and preemptive act of self-defense that averted a potentially catastrophic attack and secured vulnerable borders. In many Arab narratives, it is remembered as a result of Israeli aggression, external manipulation, and Arab military and political failure.

Disagreement persists over key questions. These include how real and imminent the threat of an Arab attack on Israel was in early June 1967, what exactly Soviet intentions were in providing the initial intelligence to Egypt, how much room existed for diplomatic solutions to the crisis, and whether different choices by leaders on any side could have prevented war.

What is clear is the sequence of events: a period of rising tensions along borders, Egyptian movements into Sinai and the expulsion of UN forces, the closure of the Straits of Tiran, defense pacts among Arab states, mobilizations, and then a rapid Israeli preemptive airstrike followed by swift ground operations on three fronts. The war’s brevity and decisiveness, combined with the major territorial changes it produced, made it one of the most consequential episodes in the modern history of the conflict.

In the chapters that follow, the focus shifts from how the war began and unfolded to the long-term consequences of these six days. Those consequences involve questions of occupation, security, diplomacy, law, and identity that still shape the realities of Israelis, Palestinians, and the wider region today.