Near the close of Israel’s election campaign last month, Prime Minister Benjamin Netanyahu made a public commitment to extend Israeli law and jurisdiction to the Jordan Valley and the Northern Dead Sea immediately following the elections. This was understood as a pledge to annex what has been viewed as probably the most important part of the West Bank when it comes to protecting Israel as a whole.

How this land came to be widely perceived as being so vital for Israel’s security is not well known. More importantly, how the Jordan Valley still remains the front line of Israel’s defense despite so many developments in military technology and Middle Eastern politics is also not well understood. What remains a constant for many years is the idea that Israel must be able to defend itself by itself and not accept external guarantees, even from the United States, in lieu of its own self-defense capabilities. This applies especially to the discussion over its retention of the Jordan Valley.

Israel captured the valley and the rest of the West Bank from Jordan in the 1967 Six Day War. Almost immediately, the Jordan Valley zone was integrated into Israel’s security system facing east. The idea that Israel was entitled to modify its borders became part of the diplomatic discourse right after combat operations ended. Israeli Foreign Minister Abba Eban wrote in his memoirs that the pre-war lines had been fashioned through armistice agreements that were based on military considerations; they were not international political borders. New borders were required.

This was enshrined in the language of UN Security Council Resolution 242, whose territorial clause did not insist upon a full Israeli withdrawal to the old armistice lines. Reference was made to an Israeli withdrawal “from territories,” but not “all the territories,” to new lines that needed to be “secure boundaries.” Britain’s Ambassador to the UN at the time, Lord Caradon, who helped draft UNSCR 242, commented on PBS: “We all knew—the boundaries of ’67 were not drawn as permanent frontiers.” Replacing the previous military lines with new international borders opened the door for revising the pre-war lines.

The most important advocate of the Jordan Valley as Israel’s new front line was the Deputy Prime Minister at the time, Yigal Allon, who in 1948 had served as the commander of the Palmach, the elite pre-state strike force. His deputy was a young commander named Yitzhak Rabin. Allon emerged as his mentor, and when Rabin served as Prime Minister, a portrait of Allon hung on a wall in Rabin’s office.

Immediately after the Six Day War, Allon became the architect of a plan to initiate a string of mostly agricultural settlements in the Jordan Valley and along the hills that dominate it. Today, nearly 30 Israeli settlements are situated in this area. Allon’s map became known as the Allon Plan.

Prior to 1967, the old armistice line with the Jordanians left Israel extremely exposed. Only nine miles separated the West Bank city of Tulkarm from the Israeli city of Netanya on the Mediterranean Sea. It did not require a stretch of the imagination to consider that an invading army from the east could slice Israel in two at this point. Israeli planners needed to avert such a scenario.

Israel’s structural problem in providing for its own defense has been the gross asymmetry between its own standing forces and those of its neighbors. Whereas the Arab states were able to form multi-state war coalitions, Israel fought alone. Moreover, the Arab states organized their armies in active service formations, while the Israel Defense Forces (IDF) were structured around mostly reserve units. In short, to match the quantitative superiority of its neighbors, Israel had to mobilize its reserve forces, which required up to 48 hours.

The terrain Israel captured in the West Bank, particularly in the Jordan Valley, provided Israel with a formidable barrier for the first time that would allow the IDF to absorb an attack and buy the precious the time it needed to complete its reserve call-up. How did this exactly work? To Israel’s east is the Hashemite Kingdom of Jordan. Alone, Jordan did not constitute an existential threat to Israel. Moreover, the Jordanians signed a formal treaty of peace with Israel in 1994.

Israel’s eastern challenge historically has come from other states that exploited Jordan as a platform to attack Israel. Thus in 1948 and 1967, an Iraqi expeditionary force, made up of one third of Iraq’s ground order of battle, crossed Jordan to attack Israel. (In 1973 that same expeditionary force decided to cross Syria, instead, and attack the IDF in the north.) Today, there are still multiple sources of instability to Israel’s east. For example, Iran projects its military power across the region through fully equipped Shiite militias which it has used successfully to defeat conventional armies in Syria and Iraq.

YouTube screen capture, Jerusalem Center for Public Affairs

What the Jordan Valley gave Israel was not strategic depth, but rather strategic height. It is important to recall that the area where the Jordan River pours into the Dead Sea is the lowest point on Earth; it lies 1,300 feet below sea level. But this area is also adjacent to the steep eastern slopes of the West Bank mountain ridge that reach a maximal height of 3,300 feet. When taken together, the lowest parts of the Jordan Valley and its mountain ridge form a virtual strategic wall with a net height of 4,500 feet.

This steep barrier provided a daunting challenge for armored and mechanized units, which started to be employed widely at that time by modern armies in the Middle East. In 1973, with the IDF fully engaged in combat along two fronts on the Golan Heights and in the Sinai Peninsula, Israel had only small formations left to defend the hilly terrain of the West Bank from a ground assault. It was instructive that the Jordanians did not open this front, but rather sent their forces instead to the Golan area, where they could supplement the Syrians and the Iraqis.

In the years that followed, Israel continued to adhere to a military doctrine that viewed the Jordan Valley as a vital building block for its defense. Even after the Oslo Agreements were signed between Israel and the Palestine Liberation Organization (PLO) in 1993, Prime Minister Yitzhak Rabin reiterated a vision for a final peace settlement that kept the Jordan Valley under Israel. In a speech before the Knesset (Israel’s Parliament) on October 5, 1995, Rabin declared: “The borders of the State of Israel, during the permanent solution, will be beyond the lines which existed before the Six-Day War. We will not return to the 4 June 1967 line.”

Rabin gave special treatment to the Jordan Valley in the same speech. He emphasized that “the security border of the State of Israel will be located in the Jordan Valley, in the widest meaning of that term.” Rabin wanted to be certain that the geography he was describing was understood. He was not defining the Jordan Valley according to the width of the Jordan River alone. He did not want a future Israeli border extending right up to the water’s edge. What he had in mind was Israel continuing to control the high ground along the eastern slopes of the mountain ridge that descended down to the Jordan River. Israel named the north-south route that ran along this high-ground the Allon Road. It served as a reminder that the Allon Plan was not just about the Jordan River alone.

Israelis learned another context for appreciating the principles of the Allon Plan. In October 1976, serving as Israel’s Foreign Minister, Allon wrote an article in Foreign Affairs, entitled “Israel: The Case for Defensible Borders.” It essentially laid out the strategic logic of his plan. While there were those who asserted that in an era of advanced military technology, territory had lost its importance, Allon was convinced that wars were still decided by the movement of land armies. He wrote: “. . . as far as conventional wars are concerned, the following basic truth remains: without an attack by ground forces that physically overrun the country involved, no war can be decisive.” As long as that was the case, he believed that factors like topography, terrain, and strategic depth were still very much determinants of Israeli national security.

Allon also explained that any territory from which Israel would withdraw in the West Bank would have to be demilitarized. The question he posed was how demilitarization would be ensured. There was an arid zone, which included the Judean Desert, to the east of where the bulk of the Palestinian population lived. Allon estimated that this security zone was about 700 square miles. Thus he offered a second argument for Israel retaining the line he proposed that ran above the Jordan River. That line would safeguard the demilitarization regime that he had in mind.

Why such a line was absolutely essential was demonstrated in 2005, when Prime Minister Ariel Sharon implemented his unilateral Disengagement Plan from the Gaza Strip, which involved a full withdrawal from the area. Critics of the plan, like former Deputy Chief of Staff, General Uzi Dayan, stressed that Israel should at least retain the border zone between the Gaza Strip and Egyptian Sinai, known in Israeli parlance and the Philadelphi Route. What clearly happened in the aftermath of the Israeli pullout was a massive increase in weapons smuggling by Hamas and other Palestinian terror organizations from Egypt into the Gaza Strip. This directly influenced the rate of rocket fire on Israel.

For example, in 2005, the year of the Gaza Disengagement, a total of 179 Palestinian rockets were fired on Israeli territory. One might have anticipated that following the Israeli withdrawal the number of rocket attacks would drop sharply, along with the motivation to fire on Israel. But the exact opposite occurred: In 2006, Palestinian rocket attacks on Israel shot up to 946—more than a 500 percent increase in the rate of rocket fire. By 2008, 1,730 rockets were fired from the Gaza Strip into Israel. Hamas had built a system of tunnels over the years that allowed the Palestinian terror organizations to smuggle enormous quantities of rockets and even shoulder-fired anti-aircraft missiles. Three wars resulted from this escalation in Palestinian rocket fire.

The Jordan Valley was to the West Bank what the Philadelphi Route was to the Gaza Strip. It was the outer perimeter of the territory and adjacent to a neighboring Arab state. In the case of Gaza, Palestinian terror groups not only smuggled weaponry, they also built up for themselves a military presence in Northern Sinai which began to work closely with ISIS and ultimately undermined Egyptian sovereignty in that area. The Egyptian Army soon faced a counterinsurgency campaign on its own territory. By analogy without Israel in control of the Jordan Valley, a similar process could be expected within Jordan itself.

The main factors which worked against Israel’s position in the Jordan Valley were diplomatic. To the extent that Israeli elites believed that a negotiated settlement was around the corner, the political leadership in Israel became prepared to consider jettisoning Rabin’s legacy. This occurred during the negotiations at Camp David in 2000, under Prime Minister Ehud Barak, and several years later during the talks that were held by Prime Minister Ehud Olmert with Palestinian Authority President Mahmoud Abbas.

There was also U.S. input in this process. In early 2001, President Bill Clinton issued the “Clinton Parameters,” which summarized the negotiations held by Israel and the Palestinians. The Jordan Valley was not allocated to Israel. In 2014, General John Allen, who retired after commanding U.S. forces in Iraq and Afghanistan, worked on a security model for the Jordan Valley predicated on an Israeli pullback.

But the Israeli public was not persuaded by what their elites were prepared to consider or by the newest U.S. proposals. The idea that the latest military technology or international forces could reliably replace the Israeli Army did not move most Israelis.

Israeli public opinion clearly internalized the importance of the Jordan Valley for Israeli security. In the last decade, massive majorities of Israeli voters, reaching as high as 81 percent, stated that in any peace arrangement Israel must preserve its sovereignty over the Jordan Valley (polling commissioned by the Jerusalem Center for Public Affairs, executed by Dahaf and Midgam). The support for the Jordan Valley appeared at times to rival the support for retaining a united Jerusalem. In a county whose politics have been extremely polarized, the Jordan Valley stands out as an area where a strong national consensus has prevailed.