Twenty-Five Years On, the Lessons of 9/11 Are Still Being Learnt

The first duty of a government, countless leaders have said over the decades, is to safeguard its population. On 11 September 2001 the United States manifestly failed to do that. The intelligence was there, yet tragically nobody joined up the dots in time. The attacks that followed came to define, along with the response, a generation of foreign, security and intelligence policy for the first two decades of this century.

On that cloudless September morning, as al-Qaeda's suicide pilots flew hijacked planes into the World Trade Center, this correspondent was finishing a deployment in the Middle East bureau. A Palestinian taxi driver, driving through the pine-clad hills west of Jerusalem towards Tel Aviv's Ben Gurion airport, suddenly turned up the car radio. Something big has happened in America, he said. He was not exaggerating. Some 2,977 victims died that day.

The attacks did not come out of nowhere. The CIA had been aware of the al-Qaeda network and its exiled Saudi leader, Osama Bin Laden, for years before 2001. It even had a taskforce dedicated to hunting him down. Nine days after the attacks, President George W. Bush declared the War on Terror. In the 25 years since, there have been numerous intelligence successes as well as failures on both sides of the Atlantic. Plots have been foiled; suspects have been arrested, tried, convicted and jailed.

No one can question that 9/11 was a colossal intelligence failure. More precisely, it was a failure of imagination in the US intelligence community. At the time, both the CIA and the FBI held information which, if shared properly, could have prevented what happened. The 9/11 Commission Report blamed failures of imagination, policy, capabilities and management on the US government. The CIA and FBI, it concluded, failed to assess intelligence properly, share it with each other and take sufficient steps to disrupt the plot.

That most basic of lessons has since been largely, though not completely, learnt. Sharing between Western intelligence agencies is infinitely better than it was in 2001. The old rivalries between MI5 and police counter-terrorism have dissolved, first with regional fusion centres dotted around the UK and now with the high-security Counter Terrorism Operations Centre in London. There, MI5 intelligence officers may find themselves sitting beside police officers whose job is to take executive action to stop a plot, or beside a US federal agent from the FBI or a language specialist seconded from GCHQ.

Since 9/11 there has also been a root-and-branch reorganisation of US intelligence, with a National Counter Terrorism Center just outside Washington DC and a Director of National Intelligence to ensure information is shared among the 18 separate US agencies. The relationship between the CIA and its UK counterpart, the Secret Intelligence Service, better known as MI6, is perhaps the closest in the world, supplemented by the Five Eyes alliance that pools intelligence between the US, UK, Canada, Australia and New Zealand.

Yet disastrous failures of intelligence, assessment and strategic planning have still occurred since the planes hit the Twin Towers. In the run-up to the US-led invasion of Iraq in 2003, MI6 unwisely allowed its intelligence to be politicised, leading to its worst reputational setback since the betrayal by the double agent Kim Philby and other Soviet moles in the 1950s and 1960s. Against overwhelming political pressure from Washington to produce evidence that Iraq under Saddam Hussein still possessed weapons of mass destruction, MI6 supplied Tony Blair's government with what turned out to be flawed intelligence. Iraq had indeed possessed such weapons in the past, but they were destroyed after the 1991 Gulf War.

Following the invasion, MI6 revamped how it assesses the raw intelligence, known as CX, that comes from agents in the field. Today there is a clear separation between the agent runners, who gather intelligence from sources in places like Iran and North Korea or from inside proscribed groups such as al-Qaeda, and the reports team, whose job is to check and challenge that intelligence, often sending it back to demand more substantiation. General Sir Richard Shirreff, who served in Iraq as a divisional commander, said the war was based on deeply flawed intelligence. Have we learnt from it, he asked. No, I think we are bad at learning. It was so obvious as a commander that we were heading for strategic failure. The subsequent Butler Review concluded that the UK's intelligence on Iraq's alleged weapons programme was seriously flawed and heavily reliant on unverified sources.

MI5 has also had its failures, amid numerous undoubted successes in foiling plots. Lord Jonathan Evans, who ran the Security Service from 2007 to 2013, said the assessment after 9/11 was that by far the most pressing security threat to the UK was the terrorist threat from al-Qaeda and associated individuals and groups. But with a database of more than 20,000 subjects of interest and many investigations running concurrently, MI5 faced, and still faces, a daily challenge of deciding which leads to prioritise. It has not always got it right. In 2005 it failed to prevent the 7/7 London suicide bombings that killed 52 people. The Security Service was aware of Mohammed Sidique Khan, who turned out to be the ringleader, but not of what he was about to carry out. The Manchester Arena bombing of 2017 was another lapse.

Today the threat from terrorism has not gone away, but Lord Evans says the picture has changed. Non-state terrorism remains a serious concern, he says, but state threats have become increasingly serious and are at least as severe a national security concern. These threats come, in different forms, from Russia, Iran, their proxies and from China. It could also be argued that President Donald Trump's decision to join Israel in attacking Iran this year was a failure of intelligence imagination. All America's allies in the Gulf knew there was a serious risk Iran would retaliate by closing the Strait of Hormuz. The warnings were all there, yet Trump appeared to lack a counter-strategy when Iran did exactly what it had threatened, causing huge disruption in global energy markets.

In the immediate aftermath of the attacks there was widespread fear that a second wave was coming. Al-Qaeda itself promised a swarm of planes that would attack more buildings. In the rush to pre-empt such an attack, numerous human rights abuses were committed by the US and its allies. Suspects were swept up in Afghanistan or Pakistan, often on the flimsiest of tip-offs. Hundreds were flown, bound, blindfolded and wrapped in nappies, halfway across the world to a makeshift cage prison at the US naval base in Guantanamo Bay, Cuba, where they were held without trial. Human rights groups denounced this as a stain on the moral conscience of America.

Scandals over the abuse of prisoners in US custody in Iraq and Afghanistan have duly come to light, and some of those involved have been held to account, though critics say more senior figures escaped consequences. The US still practises detention without trial at Guantanamo Bay, and in 2025 it deported more than 200 men to El Salvador's controversial Terrorism Confinement Centre. The period after 9/11 left stains on human rights in Britain too. In 2004, MI6 was complicit in the abduction and rendition of a Libyan Islamist, Abdelhakim Belhaj, and his wife from Thailand to Libya, where he spent years in prison and was tortured by Colonel Muammar Gaddafi's regime. The case eventually came to light, resulting in a fulsome public apology delivered to Parliament by the Attorney General in 2018. Today, in-house lawyers are said to be the fastest-growing department within the agencies.

Sir Alex Younger, Chief of the Secret Intelligence Service from 2014 to 2020, said the West spent the first 20 years of this century focusing almost entirely on counter-terrorism and counter-insurgency. Speaking shortly after leaving the top job, he added that we missed the rise of China as a military power and as a strategic challenge. General Shirreff, for his part, wrote the political thriller War With Russia in 2016, in which he foresaw Russia's full-scale invasion of Ukraine.

In the aftermath of 9/11 and the ensuing War on Terror, while Western nations fought the Taliban, ISIS or tried to sort out the messy occupation of Iraq, Russia and China embarked on colossal rearmament programmes, with innovations in hypersonic missiles that have seriously eroded the military advantage once enjoyed by Nato. Sam Olsen, chief analyst at the security intelligence firm Sibylline, argues that the West's mistake was not simply that it was distracted by counter-terrorism. It also misunderstood the nature of China's rise, assuming that economic integration would lead to political convergence.

China, like Iran, Russia and North Korea, is considered a hard target for intelligence gathering. In 2001 biometric data was still in its relative infancy, but the subsequent use of facial, iris and gait recognition has contributed to the considerable modern-day challenge of getting agents and agent runners across borders undetected. Along with Russia, China is today a top intelligence target for MI6. Mr Olsen says Western intelligence understands a great deal about China, but the bigger danger is that it sees the individual pieces without always understanding what they add up to. Chinese power, he notes, is no longer just about ships, missiles and troops. It increasingly lies in semiconductors, critical minerals, batteries, ports, telecommunications and industrial capacity. The problem is often less a failure of intelligence collection than a failure of strategic interpretation.

Twenty-five years ago, on the day of the attacks, US intelligence agents did hold pieces of the jigsaw, an analogy spies love to invoke. Collectively, they failed to fit it together and see clearly what was coming down the tracks. It is no good having great intelligence gathering if you cannot apply it for strategic gain. The world of intelligence and counter-terrorism has changed almost beyond recognition in the quarter century since that cloudless blue September morning in New York. With the advent of AI and quantum computing it will only go on changing, in some areas at exponential speed.

In a world full of conflicting narratives and interests, Western nations do not have a monopoly on failures of intelligence, oversights or strategic miscalculations. Other noteworthy instances include Russia's disastrous full-scale invasion of Ukraine in 2022 and what some have described as Israel's own 9/11, the Hamas-led raid from Gaza on 7 October 2023. Ultimately, it is in the big, strategic, national decisions that questions are still being asked. Was it right for Britain to join President Bush's invasion of Iraq? Was it right to join the US-led Operation Enduring Freedom in Afghanistan and then abandon the country to the Taliban in a dash for the exit two decades later? These, and many other questions, continue to reverberate.