The Six-Day War, or the 1967 Arab–Israeli War, was fought between June 5 and June 10, 1967, by Israel and the neighboring states of Egypt (known then as the United Arab Republic, UAR), Jordan, and Syria. The origins of the war include both longstanding and immediate issues. At the time of the war, the earlier foundation of Israel, the resulting Palestinian refugee issue, and Israel's participation in the invasion of Egypt during the Suez Crisis of 1956 continued to be significant grievances for the Arab world. Arab nationalists, led by Egyptian President Gamal Abdel Nasser, continued to be hostile to Israel's existence and made grave threats against its Jewish population. By the mid-1960s, relations between Israel and its Arab neighbors had deteriorated to the extent that a number of border clashes had taken place.

In April 1967, Syria shot at an Israeli tractor ploughing in the demilitarized zone, which escalated to a prewar aerial clash. In May 1967, following misinformation about Israeli intentions provided by the Soviet Union, Egypt expelled UN peacekeepers who had been stationed in the Sinai Peninsula since the Suez conflict, and announced a blockade of Israel's access to the Red Sea (international waters) via the Straits of Tiran, which Israel considered an act of war. Tension escalated, with both sides' armies mobilising. Less than a month later, Israel launched a surprise strike which began the Six-Day War.

The conventional view has long suggested that Israel's actions leading into the war were prudent, laying the blame for the war on Egypt. According to political scientist Zeev Maoz, most scholarly studies now attribute the crisis to a complicated process of unwanted escalation, which all sides wanted to prevent, but for which all were ultimately responsible.Maoz, Zeev. Defending the Holy Land: A Critical Analysis of Israel's Security & Foreign Policy, p. 111 (University of Michigan Press, 2009): "It is most important to reiterate the conclusion of most scholarly accounts of the crisis: this was a process of unwanted escalation, which everybody wanted to prevent, but all were responsible for making this escalation unavoidable." Nasser knew that his blockade of the Straits of Tiran from Israeli vessel passage, on 23 May 1967, might very likely provide Israel with reason to launch an attack. His decisions to ask for the removal of the UN peacekeepers from Sinai and especially to block the Gulf of Aqaba to Israeli shipping via the Straits of Tiran are commonly accepted as the point where war became inevitable. Many commentators consider the war as the classic case of anticipatory attack in self-defense, but some 21st century historians contest the view that Israel acted in self-defense.

Summary of events leading to war After the 1956 Suez Crisis, Egypt agreed to the stationing of a United Nations Emergency Force (UNEF) in the Sinai to ensure all parties would comply with the 1949 Armistice Agreements.Rauschning, Dietrich; Wiesbrock, Katja & Lailach, Martin (eds.) (1997). Key Resolutions of the United Nations General Assembly 1946-1996. Cambridge University Press. .Sachar 2007, pp. 504, 507–8. Despite the overwhelming support for Resolution 1000 in the UN General Assembly (UNGA), Israel refused to allow UNEF forces onto its territory. In the following years, there were numerous minor border clashes between Israel and its Arab neighbors, particularly Syria. In early November, 1966, Syria signed a mutual defense agreement with Egypt.Some sources date the agreement to November 4, others to November 7. Most sources simply say "November". Gawrych (2000) p. 5. On November 13, 1966, in response to PLO (Palestine Liberation Organization) guerrilla activity,Schiff, Zeev, History of the Israeli Army, Straight Arrow Books (1974) p. 145.Churchill & Churchill, The Six Day War, Houghton Mifflin Company (1967) p. 21. including a mine attack that left three dead,Pollack, Kenneth, Arabs at war: military effectiveness 1948-1991, University of Nebraska Press (2002), p. 290. the Israeli Defence Force (IDF) attacked the village of as-Samu in the Jordanian-occupied West Bank.Segev, 2007, pp. 149–52. Jordanian units that engaged the Israelis were quickly beaten back.Hart, 1989 p. 226. King Hussein of Jordan criticized Egyptian President Gamal Abdel Nasser for failing to come to Jordan's aid, and "hiding behind UNEF skirts".Oren 2002/2003, p. 312.Burrowes & Douglas 1972, pp. 224–25. Israel was censured for this invasion in United Nations Security Council Resolution 228, being reproached by the US, the UK, France and the USSR. On April 7, 1967, tensions between Israel and Syria escalated into a major military engagement after Syrian forces fired on an Israeli tractor in the demilitarized zone. This led to a large-scale air battle in which the Israeli Air Force shot down six Syrian MiG-21 fighter jets, some over Damascus. In May 1967, Nasser received false reports from the Soviet Union that Israel was massing on the Syrian border.

Nasser began massing his troops in the Sinai Peninsula on Israel's border (May 16), expelled the UNEF force from Gaza and Sinai (May 19) and took up UNEF positions at Sharm el-Sheikh, overlooking the Straits of Tiran.Shlaim (2007) p. 238.Mutawi (2007) p. 93. Israel reiterated declarations made in 1957 that any closure of the Straits would be considered an act of war, or justification for war.Cohen, Raymond. (1988), p. 12. Nasser declared the Straits closed to Israeli shipping on May 22–23. On May 30, Jordan and Egypt signed a defense pact. The following day, at Jordan's invitation, the Iraqi army began deploying troops and armored units in Jordan.Churchill pp. 52, 77. They were later reinforced by an Egyptian contingent. On June 1, Israel formed a National Unity Government by widening its cabinet, and on June 4 the decision was made to go to war. The next morning, Israel launched Operation Focus, a large-scale surprise air strike that launched the Six-Day War.

Territorial, water ways and water resources disputes

Territorial disputes The peace accord at the end of the 1948 war had established demilitarized zones (DMZs) between Israel and Syria. However, as recalled by UN military forces officers such as Odd Bull and Carl von Horn, Israelis gradually took over portions of the zone, evicting Arab villagers and demolishing their homes; these actions incurred protests from the UN Security Council. Moshe Dayan, the Israeli defense minister at the time of the Six Day War, recounted in a 1976 interview that Israeli policy in the Demilitarized Zone between 1949 and 1967 was "to seize some territory and hold it until the enemy despairs and gives it to us", thus changing "the lines of the ceasefire accord with military actions that were less than a war". See also Shlaim 2001, pp. 235-236; Eyal Zisser, June 1967: Israel's capture of the Golan Heights, Israel Studies, Vol 7, 168-194. Dayan related further that in the process Israel had provoked more than 80% of the border clashes with Syria in the lead-up to its April 7, 1967 invasion of Syria. In defense of the Israeli actions historian Michael Oren said that "[t]here is an element of truth to Dayan's claim", but that Israeli actions were justified, as "Israel regarded the de-militarized zones in the north as part of their sovereign territory". Gluska qualified this view by pointing out that such Israeli sovereignty over all of the DMZ "was not sanctioned by the UN".Gluska, Ami. "The Israeli Military and the 1967 War", Routledge, 2007, p. 40 In fact the Israeli view had been rejected in 1951 by both Britain and the UN Security council (in Resolution 93).Sitta, The Line of 1967-1949 , Part 3 - "The mysterious line of June 4, 1967", October 1999 In January 1967 Israel reverted to claiming sovereignty over the DMZ.Gluska, Ami. "The Israeli Military and the 1967 War", Routledge, 2007, p. 95

Publicly, Syria claimed that the escalating conflict was the result of Israel attempting to increase tension in order to justify a large-scale military operation against Syria, and to expand its occupation of the Demilitarized Zone by dispossessing the remaining Arab farmers.

According to Moshe Shemesh, a historian and former senior intelligence officer in the IDF, Jordan's military and civilian leaders estimated that Israel's main objective was conquest of the West Bank. They felt that Israel was striving to drag all of the Arab countries into a war. After the Samu raid, these apprehensions became the deciding factor in Jordan's decision to participate in the war. King Hussein was convinced Israel would try to occupy the West Bank whether Jordan went to war, or not.Shemesh 2008, p. 117

Straits of Tiran On May 23, 1967, Egypt (UAR) announced the closure of the Straits of Tiran to all Israeli flagged vessels, as well as to all vessels containing strategic materials bound for Israel: "The Israeli flag shall not go through the gulf" said UAR President Nasser.

Water dispute

The Johnston Plan was a plan for the unified water resource development of the Jordan Valley, sponsored by UNRWA and accepted by the main Arab leader, Nasser, and by Jordan and Israel. In 1964, Israel began drawing water from the Jordan River for its National Water Carrier, in accordance with the Johnston Plan, reducing the flow that reached Hashemite territory to the Johnston Plan allocation.Sosland, Jeffrey (2007) Cooperating Rivals: The Riparian Politics of the Jordan River Basin, SUNY Press, p 70 In January 1964 an Arab League summit meeting convened in Cairo, claimed that the diversion of the Jordan waters by Israel multiplies the dangers to Arab existence and decided to deprive Israel of 35% of the National Water Carrier capacity, by a diversion of the Jordan River headwaters (both the Hasbani and the Banias tributaries) to the Yarmouk River, although the scheme was only marginally feasible, it was technically difficult and expensive. The following year, the Arab states began construction of the Headwater Diversion Plan, which, once completed, would divert the waters of the Banias Stream before the water entered Israel and the Sea of Galilee, to flow instead into a dam at Mukhaiba for use by Jordan and Syria, and divert the waters of the Hasbani into the Litani River in Lebanon.Oren 2006, p. 135. The diversion works would have reduced the installed capacity of Israel's carrier by about 35%, and Israel's overall water supply by about 11%.

The Israel Defense Forces (IDF) attacked the diversion works in Syria in March, May, and August 1965, perpetuating a prolonged chain of border violence that linked directly to the events leading to war.Koboril and Glantz 1998, pp. 129–131.

Events during the years before the war

Israel and the Arab states At the time, no Arab state had recognized Israel. Syria, aligned with the Soviet bloc, began sponsoring guerrilla raids on Israel in the early 1960s as part of its "people's war of liberation", designed to deflect domestic opposition to the Ba'ath Party.Rabil 2003, pp. 17–18.

Speaking to the UN General Assembly in September 1960, Nasser had stated that "The only solution to Palestine is that matters should return to the condition prevailing before the error was committed — i.e., the annulment of Israel's existence." In 1964 he said, "We swear to God that we shall not rest until we restore the Arab nation to Palestine and Palestine to the Arab nation. There is no room for imperialism and there is no room for Britain in our country, just as there is no room for Israel within the Arab nation." In 1965 he asserted, "We shall not enter Palestine with its soil covered in sand, we shall enter it with its soil saturated in blood."Sachar, 2007. pp. 615–16.