A senior Israeli air force commander was asked recently how he would feel if, like his predecessors 50 years ago, he had to launch a strike against enemy targets using over 90 per cent of the air-force’s jet-fighters and leaving only 12 interceptors to guard the country’s airspace.

He smiled and answered that he did not believe Israel would be in the situation where it has to take such a gamble again. Then he thought for a moment and said: “Yes, if we have so much at stake, we’ll take the risk again. Don’t forget, we had intelligence and planning. That’s what the air force is prepared to do.”

With hindsight, all military victories, no matter how surprising and harebrained they may have looked at the time, can be explained rationally.

In Israel’s War of Independence, the newborn state succeeded in fighting five Arab nations, in addition to the local Arab gangs within Mandatory Palestine and a force of volunteers raised from across the Arab World.

The Jewish militias that were combined into the new Israel Defence Force were outnumbered and outgunned but, with historical hindsight, their victory makes sense.

David Ben-Gurion had directed the pre-state Hagana to start preparing for this war three years earlier. Millions of dollars had been raised from American-Jewish philanthropists to purchase heavy weapons and the machinery for a local arms industry.

Despite the political rivalries within the Zionist movement, the Jewish forces were well-coordinated and resources and personnel were directed to where they were needed most. The Jewish Yishuv was fully enlisted in the war effort. What it lacked in numbers, it made up for in superior planning.

The Arab forces suffered from discord within their ranks. The local Palestinian population had a bitterly divided leadership and the Arab governments were suspicious of each other’s intentions and reluctant to commit large forces as a result.

When the war ended in early 1949, the only Arab force to have made significant gains was Jordan’s British-trained and equipped Arab Legion, which occupied the West Bank and East Jerusalem.

Eight years later, Israel won its second war, sweeping the Egyptian Army from the Sinai Peninsula in the operation which provided Britain and France with the pretext for their disastrous Suez Campaign of 1956.

In 1967, in addition to superior planning, there was surprise. The Six-Day War combined a well-planned surprise strike with what would become the hallmark of all successful operations — detailed intelligence.

Throughout the 1960s, Mossad and the IDF’s military intelligence burrowed away beneath the Arab military establishment, creating a complete picture of its capabilities. The pilots taking off early on the morning of June 5 to take out the Egyptian air bases knew exactly where their targets would be situated, and even which of the aircraft on the ground were decoys. Should any enemy pilot take off before they arrived, they had already learned the capabilities and vulnerabilities of the most advanced Soviet fighter, the Mig-21, after an Iraqi pilot defected with his aircraft to Israel in a Mossad-orchestrated operation.

As Israeli aircraft reached their targets, the order was given to the ground columns to start advancing into Sinai. The tank and infantry officers also knew where to expect enemy resistance, the types of Russian tanks they would face and how to destroy them.

In just over two decades, from the pre-independence years to the eve of the Six-Day War, a military DNA had been established that ensured Israel’s survival in a hostile environment. Planning, coordination, detailed intelligence, the element of surprise had all been combined with another crucial element — technological superiority. Not just the most advanced weaponry Israel could buy from its main supplier at the time, France, but also a home-grown defence industry producing tailor-made solutions — from airstrip-destroying bombs to radar-jamming equipment and computers for collating and analysing intelligence. And, of course, the ultimate insurance policy: Israel’s nuclear programme.

The Six-Day War remains key to the history of the Middle East, not just because of the far-reaching implications of Israel’s conquests of Sinai, East Jerusalem, the Golan Heights and the West Bank, but because it proved that the two previous wars were no fluke.

The Israeli military doctrine, playing to the strengths of a small, resourceful population that could be mobilised at short notice, was proven effective at fighting modern armies on three separate fronts. It made sense. And despite its limitations — chiefly that it did not predict the actions of Arab leaders, missing Egyptian President Gamal Abdel Nasser’s deployment of his army to Sinai in May 1967 and the joint Egyptian-Syrian surprise attack in October 1973 — it still had the flexibility to respond swiftly and move the battle to the enemy’s territory.

Six days of war on three fronts proved that as long as Israel maintained a clear intelligence picture of its enemies’ capabilities, retained a small, well-trained standing army and a larger reserve one that could be mobilised at short notice, and continued to invest in maintaining a technological advantage, any Arab plans for Israel’s destruction would remain illusory.

Israel was to fight one more conventional war against Arab armies in 1973, but despite the rhetoric from Cairo and Damascus and a temporary atmosphere of desperation on the Israeli side, it never doubted Egypt and Syria were trying to do anything more than to regain some of their lost pride and territory from 1967. Not annihilate the Jewish state.

Victory in the Six-Day War meant Israel’s survival was never again in question. It also meant it had to embrace a new set of security challenges and dilemmas, while not abandoning the military doctrine that ensured survival to begin with.

This has led to a series of contradictions. Peace with Egypt and Jordan and the more recent disintegration of Syria has allowed Israel to steadily decrease the size of its conventional ground force, particularly the number of armoured brigades. But the need to retain conventional capabilities should the regional situation drastically change, while facing Palestinian terror organisations, Lebanon’s Hezbollah and other jihadist movements which filled the vacuum left by the Arab states, still means that a country of eight million has to have one of the largest militaries in the world.

The IDF is capable of fielding more main battle tanks than the combined armies of the UK, France and Germany. The IAF flies more front-line fighter-bombers than the RAF. While most Nato members do not meet the alliance standard of spending two per cent of their GDP, Israel’s defence spending is still over six per cent. Granted, this is far lower than peak expenditure in the early 1970s, which stood at 16 per cent, but it is still highest in the Western world.

Meanwhile, the new challenges facing it have meant the country has had to greatly diversify its security forces. The first Palestinian intifada and the continuing unrest in the West Bank and the Gaza Strip have meant the IDF has had to dedicate much of its manpower to constabulary-style operations in Palestinian areas, necessitating the formation of new infantry battalions and putting a strain on reserve units.

The pullback from Gaza in 2006 did not allow much of a reduction as Hamas took over the Strip, and Israel still stations two full brigades on its narrow borders. Meanwhile, the unsuitability of large, manned jets for many of the urban operations Israel found itself fighting in the West Bank, Gaza and against Hezbollah in South Lebanon led it to greatly expand the squadrons of unmanned aircraft.

From the late 1970s onwards, a series of attempts by enemy states in the region to build their own nuclear weapon — Iraq, Syria, Libya and Iran — have meant Israel has to continuously extend its intelligence reach, far beyond its borders, and continue maintaining entire squadrons of long-range strike aircraft and air-tankers for a once-in-a-generation mission.

The Gulf War in 1991, when over 40 Iraqi Scud missiles fell on Israeli cities, pointed at the new asymmetrical balance between Israel and its enemies. The Arabs could not hope to beat Israel on the battlefield but they could cause significant damage to civilian infrastructure and the economy.

The three major changes to Israel’s military build-up over the last quarter of a century have been the creation of a large Home Command, devoted to civil defence, a multi-layered array of anti-missile systems (Arrow, Iron Dome, David’s Sling) and dedicated cyberwarfare units necessary both to defend the country’s electronic infrastructure and to maintain the edge in intelligence-gathering.

The IDF is no longer dedicated just to ensuring Israel’s survival — that is a given. Instead, it is increasingly devoted to policing the West Bank and safeguarding the country’s civilian front and prosperity. While the investment in military technology has had significant civilian side-benefits, the need to keep defence spending at three times Western levels and to continue drafting the majority of young men and women for between two and three years remains a millstone on Israel’s economy.

The reservists coming home from the Six-Day War were certain they would never have to wear uniforms again. The Arabs would have no choice but to make peace.

Today, their grandchildren are already reservists and Israel may not be in existential danger, but it still has to work hard at preserving its security and prosperity.

In 1967, Israel faced an enemy axis of Sunni nations and, as hard as it is to imagine today, Iran was a strategic ally. Fifty years later, Israel is a tacit ally of the Sunni group facing the Iran-led Shia axis, with the Saudis and Egyptians at its centre. The threat has changed shape. It has not gone away.

Read all our coverage of the fiftieth anniversary of the Six Day War' here