The legacy of the Yom Kippur War, forty years on, helps explains why Israel is wary of trusting others to stand by it in time of need.
Both Egypt and Israel are remembering this week the 40th anniversary of the 1973 Yom Kippur War. Commemorations in Egypt have been a spark for deadly clashes between the army and Muslim Brotherhood supporters. Meanwhile in Israel, octogenarian ex-intelligence generals continue to publicly blame each other for the failures that allowed a massive Syrian-Egyptian attack - carried out on the holiest day of the Hebrew calendar - to take them by surprise.
Over the past month Israeli media has been flooded with reminiscences of a moment when Israel felt perhaps more vulnerable than at any point since its founding. In a rare moment of despair in the early period of the war, Israel's legendary military commander Moshe Dayan feared openly that they were facing "the fall of the Third Temple", meaning that the survival of the state itself was in the balance.
It is debatable whether the situation was ever quite that grave. But shocked by the success of Syria and Egypt's initial attack, with a combined invasion force of more than 2000 tanks, Israel's leaders could not know that at the time. It took an enormous effort and considerable cost in lives for Israel to turn the tide, ultimately regaining most of its losses and advancing on Cairo and Damascus when a ceasefire was called three weeks later.
Many recall that a massive airlift of fresh arms and equipment from the US was critical to Israel's success. But it took the US many long days to take that decision - whilst Israel's losses mounted - as Washington weighed a range of geopolitical calculations, including détente with the Soviet Union and their relations with Arab states.
Where was Britain at that moment? During the 1967 Six Day War, the Labour government of Harold Wilson had been warm towards Israel, and defended its actions. Britain was intimately involved in drafting UN Security Council Resolution 242 following the war, which linked the demand for Israel's withdrawal from captured territory to the recognition of its right to secure and recognised borders.
But in 1973, the Conservative government of Edward Heath, under the threat of an Arab oil embargo, and newly welcomed as a member of the EEC, refused to lend any assistance to Israel - imposing an arms embargo and not allowing the US planes to refuel in Britain en route to Israel. This was despite the fact that the Arab combatants were being rearmed with large airlifts from the Soviets and were supported by other Arab states. It is one of the low points in the history of the UK-Israel relationship.
The region has changed dramatically since 1973. Both Syria and Egypt are far too engrossed in their own domestic turmoil to pose a conventional military threat to Israel. Today the threats are different. But the principles the war illustrated - that Israel cannot become complacent about its security, and should always be able to protect its critical security interests by itself - remain important in Israeli political culture.
Today Israelis looks to European powers and the US to stand up in confronting Iran's nuclear programme. They debate internally whether Israel should ever contemplate taking military action without US support. In this debate, the Syrian chemical weapons saga is seen as an important case study as to the will of Western powers to get their hands dirty with the messy business of the region.
For many in Israel, the hesitation of the US and others over military action, and the leaping at the chance of a diplomatic exit, however problematic its implementation, were worrying signs. What if in the Iranian case, enthusiasm for a diplomatic deal and aversion to military action, bring the US and European powers to accept an inadequate deal, that relaxes sanctions too quickly, without pushing Iran sufficiently back from nuclear breakout capacity?
When Obama visited Jerusalem in March he told the Israeli people: 'Atem lo levad' - you are not alone. And indeed Israel does enjoy enormous strategic and political support from the US, and a shared belief that Iran should be prevented from acquiring nuclear weapons. But at a speech during Israel's commemoration of the war a few weeks ago, Netanyahu again made the case that Israel must "be able to defend itself by itself".
Without doubt when Netanyahu threatens military action against Iran he hopes to focus the minds of the US and other P5+1 powers, who fear the consequences of an Israeli strike. Nonetheless, when he told the UN General Assembly last week: "If Israel is forced to stand alone, Israel will stand alone," he sees himself drawing the lessons of Jewish and Israeli history, including the Yom Kippur War. The rest of the world should presume he means it.