The 9/11 Attacks, 20 Years On

Two decades on, we reflect on the profound impact the 9/11 attacks had on security and global strategy.

Main Image Credit World Trace Centre Tribute in Light, New York | Flicker / Dennis Leung

The attacks by the Al-Qa’ida terrorist organisation on the World Trade Centre in New York and the Pentagon on 11 September 2001 were cataclysmic in their effect on the global strategic environment.

After two major wars and a dramatic evolution of the terrorist threat, we mark the 20-year anniversary of 9/11 through a series of events, published analysis and videos.

Event Recordings

Watch the recordings of events hosted in memory of the 9/11 attacks.

Members events

The 9/11 Attacks, Two Decades On with The Rt Hon Tony Blair

The 9/11 Attacks from a Historical Perspective

9.11 Two Decades of Disruption

Dr Karin von Hippel participates in a documentary exploring the impact that the catastrophic 9.11 attacks had on the insurance industry, national security, government policy and on society.

IFTRIP, in collaboration with the US Treasury, presents 9.11: Two Decades of Disruption

Our Reflections

RUSI staff, Trustees and Distinguished Fellows share their thoughts on the impact of the 9/11 attacks, 20 years on.

Dr Karin von Hippel: The Global Consequences of the September 11 Attacks

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Suzanne Raine: Terrorism is a Long-Term Strategic Issue

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Jonathan Evans: September 11 was a Watershed Moment

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Sabin Khan: 9/11 Is A Long-Term Generational Challenge

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Professor Michael Clarke: 9/11 Marked A 'Change of Era'

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Sir Mark Rowley: Tackling Hateful Extremism Requires a Broad Approach

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Tom Keatinge: Financially Disrupting Terrorist Activity Post-9/11

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Commentary & Analysis

Access Commentary articles and external publications commenting on the impact of the 9/11 attacks

Two Decades After 9/11, Let Us Not Forget This is About People

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The British and 9/11: So Near and Yet So Far

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The War Might be Over, but ‘Yesterday’s Problem’ has Not Gone Away

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Ending the '9/11 Era': Multilateralism and the Future of Effective Counter-Terrorism

Twenty years on from the devastating 11 September attacks, RUSI Senior Associate Fellows Eric Rosand (US) and Sabin Khan (UK), experts who have worked at the heart of American and British government efforts to counter terrorism and violent extremism post-9/11 provide commentary - Global Coalition, 9 September, 2021

How the US should reestablish trust with its allies

There are two immediate opportunities to work together again on issues that matter to both the United States and the world - By Douglas Alexander, Boston Globe, September 8, 2021

The RUSI Journal Article Collection

The RUSI Journal has published extensively on the themes of terrorism and countering violent extremism over the past 20 years. We have drawn together a collection of articles that trace how our understanding has evolved since that momentous day in September 2001.

  • Terrorism did not start with the attacks of 9/11, but there can be no doubt that these events changed the way that we think and look at the phenomenon. Terrorist spectaculars in themselves were not new – Carlos the Jackal had perfected the art, while seasoned terrorism watcher Brian Michael Jenkins had coined the phrase ‘terrorism is theater’ as early as 1974. But the magnitude and ambition that Al-Qa’ida displayed seemed to change things. For security experts, it pushed what had been largely seen as a niche specialisation into the centre ground of security thinking.


    Within the research community it also engendered a new wave of thinking and research as people struggled to comprehend, explain and analyse the apparently new phenomenon that had burst on to our screens that clear September day. Much of the early discourse was an attempt to define what had just happened, both in terms of trying to comprehend who Al-Qa’ida was, but also to appropriately frame the response. The decision by the US to immediately move to a bellicose context meant a deeply conflictual stage was set early on. The decision to follow the invasion of Afghanistan with the invasion of Iraq only further complicated this discussion, steering us away from solely confronting Al-Qa’ida to taking on all adversaries out there. This muddying continues to ripple through the problems we see today.


    Yet the truth that slapped the UK brutally in the face in July 2005 was that the threat was in fact one that came from within. Already in the wake of the 9/11 attacks, the UK was shocked to discover there were young Britons fighting alongside the Taliban and Al-Qa’ida. The shoe bombers later in the year were evidence of what this could turn into. And in 2005, Londoners woke to the grim reality that these individuals were willing to come back and commit atrocities on their home soil. This exposed a key dimension that was going to be needed in the response: to find ways of better engaging with the wider communities within our societies from which these individuals came. The need for a holistic response had already been identified in 2003 in the early versions of the counterterrorism strategy CONTEST, but what this actually meant in practice and how essential this was only became apparent later.


    But the converse of this holistic, all-of-society response, was to turn everyone into a security agent. Something that rankled parts of society who felt that the approach was overly intrusive and stepping all over civil liberties which a liberal-democratic society should cherish. While politics played some role in this discourse, the reality was that much of the political establishment was largely supportive of expansive powers being given to security services in their pursuit of shielding us from violent extremists.


    The perennial conundrum this created, however, was that there was a conclusion that the problem came from within and we needed to work with Muslim communities in particular to deal with the problems. But at the same time, those very communities disliked the exaggerated negative attention they were receiving, feeling even more ostracised by the very policies purportedly developed to help them to better integrate.


    These were unfortunately not debates that were ever really resolved, and took place against the backdrop of a threat that continued to evolve and develop. From being almost entirely directed by Al-Qa’ida using bases in Pakistan drawing on the UK’s deep human connection with that country, the terrorist threat spread to places such as Somalia and Yemen. Young Britons continued to get animated by extremist ideas and were drawn to an ever-expanding range of locations to join fundamentalist groups. This broadened the range of places the research community needed to understand. But it also highlighted the deep persistence of the problem even after senior figures and camps got hammered by the increasingly far-reaching UAV (drone) strike campaigns.


    This particular tactic raised a new set of questions for the UK – around proportionality and state assassination. The US had clearly already set a path in this direction, but for the UK the discussion was a complex one which touched on a complicated history of the Irish troubles. The UAV capability provided a level of reach that was unparalleled, but it raised complicated ethical issues. Legal systems in the UK were already struggling with new legislation aiming to criminalise possession of material, ideas and conviction for acts which had not taken place.


    And then the emergence of the Islamic State from the civil war in Syria appeared to suggest the entire cycle was repeating itself once again but closer to home. There were new tweaks to the Islamic State menace, whose exceptional online presence provided researchers with an extraordinary level of data and information which they could use to analyse the threats posed by the group. Individual terrorists could be spoken to from the battlefield. Group messaging became global and accessible instantaneously, something Osama bin Laden could only dream of achieving.


    This also sharpened problems that were already emerging. The lone-actor threat had already started to appear in the UK in 2007. But by the time the war in Syria took off, it had become a more prominent part of the threat. In part no doubt as a result of an effective security response which made it harder for large-scale plots to get through, but also as a result of the fact that the ideas were now so diffuse that anyone could easily access them and react to them.


    The research discourse also started to evolve. As we moved into a time of isolated terrorists, the question of ideology and group identity started to get overtaken by research focusing on individual stories, causes and narratives. This in turn created a wave of research trying to craft the nuanced responses that would be required to deal with a problem which was as unique as each individual who had become involved. This then opened up a focus on different sub-groups – be it on the basis of gender, age or mental health. This transformed the nature of communities that researchers were focused on.


    But the grim reality is that the problem of terrorism has never really left us and is unlikely to. During this 20-year chapter defined by the opening salvo of the 9/11 attacks and closed (at least in political narrative terms) by the US withdrawal from Afghanistan, the world has gone through many contortions. The research community has found itself following and echoing these. But often the most frequent finding is that these problems are not new, the drivers are as much personal as societal, and the danger is that we continue to reinvent the wheel as we seek to find an answer to what is likely an intractable societal ill. Terrorism existed pre-9/11, and it is going to follow us deep into the future.

The RUSI Journal Article Collection: The 9/11 Attacks - Two Decades of Countering Violent Extremism

This collection of articles traces our understanding of terrorism and violent extremism since 9/11.

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Lessons for Preventing and Countering Violent Extremism: An Evidence-Based Approach