The deadly attack by Hamas on 7 October represents the greatest failure of Israeli intelligence in the country’s 75-year history. At least 1,200 Israelis have been slaughtered. But the attack was not just an Israeli intelligence failure: it was international. Citizens of other countries, including at least 17 British and 22 Americans, were killed. If it transpires, as some reports suggest, that Iran provided operational support for Hamas, then this would represent a failure on the part of other countries’ intelligence services, targeting Iran, to catch wind of the planned assault.

The attack was also, in cold operational terms, a success for Hamas. According to a senior officer from Israel’s security service, Shin Bet, whom I interviewed over the weekend: ‘nobody can understand how this happened’.

Israel now faces arguably the most perilous moment in its history. When adjusted for Israel’s population size, this attack by Hamas is worse than 9/11 was for the United States. The attack, which took place on a Jewish holiday, represents the darkest day in Jewish history since the Holocaust. The images emerging from southern Israel and Gaza, which Hamas controls, are horrendous. Hamas – which the British government designates a terrorist organisation – murdered Israeli civilians in cold blood, raped and beheaded victims, and has taken at least a hundred Israeli hostages to Gaza, one of whom is a Holocaust survivor using a wheelchair. Hamas fighters killed babies and parents in their homes. Partygoers at a music festival were slaughtered.

Israel has now besieged Gaza, with the stated intent of eliminating Hamas from existence. Doing so will involve urban warfare in densely populated streets, in which civilians will inevitably be killed. Hamas fighters do not wear uniforms. There will be a circular loss of life. Israel is preparing for a long war.

It is too early to draw any firm conclusions about how and why Israeli intelligence failed to detect and warn about Hamas’s attack. This will be scrutinised by the Israeli government in due course. But even at this early stage, some tentative observations can be offered.

Intelligence failures can arise in at least four different ways: through a breakdown of intelligence collection, through a failure of analysis, or a failure on the part of decision makers to listen to intelligence provided. An intelligence failure can equally occur when sufficient distance is not maintained between intelligence and policymaking, so that intelligence becomes politicised.

The catastrophe of US intelligence before 9/11 was, infamously, not a failure of intelligence collection, but a failure of analysis, to ‘connect the dots’ between clues indicating those terrorist attacks. Another intelligence disaster from our recent past, which still plagues Western services, was the faulty intelligence about Iraq’s Weapons of Mass Destruction (WMDs). That debacle was a perfect storm: a failure of intelligence collection, analysis, to ‘tell truth to power’, and the breakdown of safeguards so that decision-makers in Washington and London fitted intelligence about WMDs to what they wanted to hear.

Before Hamas’s attack on Israel, there was, self-evidently, a failure of Israeli intelligence collection. Israeli intelligence, principally Shin Bet and Israeli military intelligence, failed to discover Hamas’s plot from their human intelligence or technical intelligence sources in Gaza. This is surprising given the pre-eminent reputation of Israeli intelligence services, and, more specifically, considering that Gaza, the impoverished, small 360 square kilometre coastal strip wedged between the Mediterranean and Israel, is one of the most intensely surveilled places on earth. Israeli forces have extensive electronic monitoring capabilities there. Before this past weekend, the world assumed that Israel had equally extensive agent networks there. What happened?

Part of the explanation seems to be that Hamas resorted to low-tech, old-fashioned, tradecraft that foiled Israeli high-tech capabilities. Hamas achieved apparently perfect operational security: its attack was, it seems, only known to a small number of commanders, who gave orders by word of mouth, thus keeping them out of reach of Israeli eavesdroppers. Israeli security officials monitoring live feeds of the border with Gaza would not have considered anything unusual about people, who turned out to be Hamas attackers, wandering near to the border zone. It was a daily occurrence. They used bulldozers — again, commonplace in Gaza — and civilian trucks to overwhelm border security. Hamas combined this low-tech offensive with sophisticated new capabilities: denial of service attacks, in which snipers took out Israeli electronic sensors. Hamas also apparently used electronic cyber capabilities to jam communications of Israeli commands.

This attack was clearly well planned and thought through, which makes it even more surprising that Israel did not detect whispers of it beforehand.

As well as a failure of Israeli intelligence collection, to defeat Hamas operational security, there may have been a failure of analysis. Hamas’s attack comes fifty years after the failure of Israeli intelligence during the Yom Kippur War in 1973, when Israeli services failed to forewarn an attack by a coalition of Arab states led by Egypt and Syria. The Yom Kippur War has gone down in history as a textbook example of intelligence failure – a mantle that Hamas’s attack will surely now take over. At root, the Yom Kippur war was a failure of Israeli intelligence analysis: driven by a faulty belief that Arab states would not attack because of Israel’s previously demonstrated military strength. Was there a similar analytical failure before Hamas’s assault, a belief by Israeli analysts that Hamas would not attack because it had too much to lose by doing so?

What about Israeli political leadership? In due course, we shall find out what intelligence, if any, Israel’s premier, Benjamin Netanyahu, was given before the attack. Some reporting suggests that Egyptian intelligence provided the Israeli government with a warning that something big was coming from Gaza. Did Netanyahu’s government overlook this? Did Israel’s deeply divided domestic politics contribute to intelligence being overlooked? More generally, did Netanyahu prioritise the threat to Israel posed by Iran – he has made little secret of his views of Iran – over the security threat from Gaza?

The geopolitical ramifications of the Israeli-Gaza war now underway are already profound. At a conference over the weekend, organised by the Cipher Brief, a leading journal for national security professionals, Norm Roule, one of the US government’s most experienced analysts on Iran, stated that the Hamas attack has heralded a seismic shift in US foreign policy. The US government is sending its newest and most advanced aircraft carrier, the USS Gerald R. Ford, to the eastern Mediterranean to support Israel. What will happen next? Will Syria enter the conflict? What about Iran’s proxy, Hezbollah, in Lebanon? Iran’s strategy has always been to draw the US into a broader conflict in the Middle East. As long as China keeps buying Iranian oil, Iran is sitting pretty.

Meanwhile, what role, if any, did Iran and Syria’s backer, Russia, play in the Hamas attack? A war in Gaza is certainly working to Putin’s advantage, as the West’s attention shifts from Ukraine.

In due course, once the bloodshed is over, the world will have to understand the reasons for Hamas’s attack – while appreciating that reasons are entirely different to excuses. Those of us who have studied Israeli history have watched with hope as relations between Israel and Arab states have normalised through the Abraham Accords, but also with fear that unless the question of Palestine is addressed, peace for Israel will remain a mirage. In due course, once Israel’s war against Hamas is concluded, the cold, pragmatic calculation for Israel will be whether a two-state solution is advantageous for its security.