25 years after 9/11: The intelligence lessons the world is still learning

Twenty-five years ago, the United States had many of the pieces of the puzzle.

It still failed to see the picture.

On 11 September 2001, 19 al-Qaeda hijackers seized four commercial aircraft and turned them into weapons. Two planes struck the World Trade Center in New York. A third hit the Pentagon. Passengers on the fourth fought back before the aircraft crashed into a field in Pennsylvania.

A total of 2,977 people from 90 countries were killed.

The attacks changed more than America's security policy.

They reshaped intelligence agencies, policing, military planning and international relations. They also produced a question that has never really gone away:

What is the value of intelligence if governments fail to understand what it is telling them?

That question remains relevant today, 25 years after the attacks.

It is particularly uncomfortable because the warning signs were not entirely absent.

The CIA had been tracking Osama bin Laden and al-Qaeda for years. The agency had made the group a major counter-terrorism priority before September 2001. But information held by different parts of the US government was not brought together quickly or effectively enough to stop the plot.

The 9/11 Commission later described the failure in four words: imagination, policy, capabilities and management.

The deeper problem was not simply that officials lacked information. They struggled to recognise what the information meant.

That distinction has shaped the past quarter-century.

From sharing information to understanding it

The immediate lesson after 9/11 was straightforward.

Intelligence agencies had to talk to each other.

The US subsequently reorganised much of its intelligence system. The National Counterterrorism Center was created to bring together terrorism-related intelligence and support strategic planning, while the post-9/11 reforms also strengthened coordination across the wider intelligence community.

The same principle took root among US allies.

In Britain, intelligence officers and police now work far more closely than they did before 2001. The Counter Terrorism Operations Centre, opened in 2021, brings together MI5, police and other partners to work on counter-terrorism operations in real time.

The Five Eyes intelligence partnership between the US, UK, Canada, Australia and New Zealand has also become an important part of Western intelligence cooperation.

So one lesson from 9/11 has clearly been absorbed:

information trapped inside institutional silos can be as dangerous as information that was never collected.

But the past 25 years have shown that sharing information is only half the battle.

The harder task is deciding what it means.

Iraq showed that more intelligence does not guarantee better decisions

Two years after 9/11, another intelligence failure exposed a different danger.

This time the problem was not simply information being missed between agencies.

It was the danger of intelligence being interpreted in a political environment where leaders were already moving towards war.

The 2003 invasion of Iraq was justified in large part by claims that Saddam Hussein's regime possessed weapons of mass destruction.

Those weapons were not found.

A series of British investigations subsequently exposed serious problems in the intelligence and its presentation. The Intelligence and Security Committee found that important uncertainties were not adequately reflected in public assessments, while concerns raised by some intelligence officials were not passed to senior decision-makers.

The later Iraq Inquiry examined Britain's involvement in the conflict and drew on the findings of earlier investigations, including the Butler Review.

The lesson was uncomfortable.

Intelligence can be wrong.

It can also be incomplete.

And even accurate fragments can produce a disastrous decision if political leaders interpret them through assumptions they already hold.

That is why the Iraq experience remains an important part of the 9/11 legacy.

The challenge is not simply to collect more information.

It is to create enough institutional space for analysts to say:

We do not know.

Or:

The evidence does not support that conclusion.

Britain learnt the same lesson through terrorism at home

The UK experienced its own painful test just four years after 9/11.

On 7 July 2005, four suicide bombers attacked London's transport network, killing 52 people and injuring hundreds more.

British intelligence agencies had encountered information connected to two of the bombers before the attack. But investigators did not have enough information at the time to identify them as an imminent threat.

A subsequent review examined whether the attacks could have been prevented and concluded that the intelligence available before 7 July did not provide a clear basis for stopping the attack.

It was another reminder that intelligence work is rarely a simple matter of finding a name on a list.

Agencies can have thousands of people of interest, competing investigations and limited resources.

The question is always:

Who represents the greatest danger right now?

Get that calculation wrong and a genuine threat can disappear into the background.

The Manchester Arena attack in 2017 provided another painful reminder of how difficult that judgement can be.

There have also been significant successes. British authorities have disrupted major plots, including a 2006 al-Qaeda-linked aviation plot targeting flights from Heathrow.

That matters because the story of intelligence after 9/11 is not one of continuous failure.

There have been many successes.

The problem is that intelligence agencies are judged most harshly by the attacks they fail to prevent.

The moral cost of the War on Terror

The lessons of 9/11 are not confined to intelligence.

They also concern what governments do when they believe another attack may be imminent.

In the years after the attacks, the US and its allies detained terrorism suspects in Afghanistan, Pakistan and elsewhere. Some were transferred to Guantanamo Bay, where detainees were held for years without ordinary criminal trials.

Abuse of detainees in Iraq and Afghanistan later became another stain on the post-9/11 response.

Britain faced its own reckoning.

The UK Government eventually acknowledged that British actions had contributed to the detention and rendition of Libyan dissident Abdel Hakim Belhaj and his wife, Fatima Boudchar. In 2018, the government apologised to the couple and acknowledged that it had failed to do enough to reduce the risk of mistreatment.

The lesson was not that national security should be abandoned.

It was that national security cannot simply erase the law.

The stronger intelligence agencies become, the greater the need for oversight, legal safeguards and accountability.

Then the strategic focus shifted

Perhaps the most consequential lesson of the past 25 years is one that was not fully understood in 2001.

The world changed.

For much of the first two decades after 9/11, Western governments concentrated enormous resources on al-Qaeda, the Taliban, Islamic State and other militant groups.

That effort produced results. The original al-Qaeda leadership was badly weakened and Osama bin Laden was eventually killed in Pakistan in 2011 after a lengthy intelligence operation involving multiple US agencies.

But while the West was fighting wars and counter-insurgency campaigns in the Middle East and Afghanistan, Russia and China were pursuing their own long-term strategic objectives.

China expanded its military and technological capabilities.

Russia rebuilt its military and later launched its full-scale invasion of Ukraine.

The intelligence challenge therefore changed.

It was no longer only about finding a terrorist cell planning an attack.

It became about understanding countries whose power could be expressed through military force, cyber operations, economic pressure, technology, critical minerals, supply chains and influence operations.

A 2026 analysis by the Center for Strategic and International Studies argues that the post-9/11 threat environment has changed dramatically, with China, Russia, Iran and North Korea presenting challenges that are very different from those that dominated the immediate aftermath of the attacks.

That creates a new version of the old problem.

There may be plenty of information.

The question is whether policymakers can see the pattern early enough.

China is the new test of strategic interpretation

China illustrates the challenge particularly well.

Its power is not limited to tanks, aircraft or naval vessels.

It also lies in semiconductors, telecommunications, batteries, ports, industrial capacity and control over critical supply chains.

That means an intelligence service looking only for traditional military indicators can miss the bigger picture.

A country does not need to fire a missile to change the balance of power.

It can change it through technology, trade, infrastructure and control over strategic resources.

A 2026 CSIS assessment warns that China's growing capabilities now extend across conventional military power, cyber operations, artificial intelligence, space and nuclear forces.

This is the modern intelligence dilemma.

The problem may no longer be a lack of information.

It may be too much information.

The difficult part is working out which developments matter, which are temporary and which could fundamentally alter the strategic balance.

The world has become harder to read

The current US-Iran conflict offers another example of how quickly intelligence, military planning and economic security can become intertwined.

The fighting that began in 2026 has disrupted shipping through the Strait of Hormuz, one of the world's most important energy routes. Reuters reported this week that traffic through the strait remains well below normal levels as attacks and counter-attacks continue. Oil prices have moved above $100 a barrel amid fears over supply disruption.

This is not simply a military problem.

A conflict thousands of kilometres away can affect fuel prices, transport costs, food prices and inflation far beyond the battlefield.

That is another lesson governments have had to learn since 2001.

National security is no longer confined to soldiers, spies and borders.

It also runs through energy markets, computer networks, undersea cables, ports, financial systems and supply chains.

Technology has changed the spy game

The intelligence world of 2001 also looks primitive by today's standards.

Artificial intelligence can process enormous quantities of information.

Biometric systems can identify people using facial, iris and other physical characteristics.

Satellites can provide near-continuous surveillance of strategic locations.

Cyber operations can penetrate networks without a single soldier crossing a border.

And quantum computing could eventually change parts of the encryption and intelligence landscape.

But technology does not remove the oldest intelligence problem.

Humans still have to decide what matters.

A machine can identify a pattern.

A government still has to decide what the pattern means.

That distinction is crucial.

The most important lesson may be humility

Twenty-five years after 9/11, there is a temptation to tell the story as though the answers were obvious.

They were not.

The 9/11 Commission itself cautioned against judging officials solely with the benefit of hindsight. It concluded that the attacks exposed failures of imagination, policy, capabilities and management, while recognising the difficulty of understanding an unprecedented threat before it happened.

That warning remains relevant.

Russia's full-scale invasion of Ukraine in 2022 showed that military intentions can still be badly assessed.

The Hamas-led attacks of 7 October 2023 exposed serious failures in Israeli warning and preparedness.

The continuing conflict involving Iran shows how quickly assumptions about deterrence and escalation can be overturned.

Different countries, different threats, different circumstances.

But the underlying question is similar.

What are we missing?

Twenty-five years later, the lesson is still unfinished

The greatest legacy of 9/11 is not simply the creation of new intelligence agencies or the expansion of surveillance.

It is the recognition that intelligence has limits.

Agencies can collect enormous amounts of information and still miss the central threat.

Governments can possess excellent intelligence and still make poor strategic decisions.

And a country can win individual battles while losing sight of the wider objective.

That is what makes 9/11's lessons so difficult.

There is no final checklist.

No intelligence reform can guarantee that another surprise attack will never happen.

No surveillance system can eliminate uncertainty.

No military alliance can predict every strategic shift.

The real test is whether governments remain willing to question their assumptions, challenge political pressure, share information, protect civil liberties and prepare for threats that do not yet fit familiar categories.

Twenty-five years after that September morning, the world is better at collecting intelligence.

It is better at sharing it.

But the hardest lesson remains the same.

Having the pieces is not enough. Leaders still have to recognise the picture they are forming — and act before it is too late.

About the Author

Maureen Onyango is a journalist passionate about storytelling, life coaching and spiritual lessons. She studied at the Kenya Institute of Management and enjoys telling stories that inform, inspire and empower communities.