By Prof. Duško Tomić and Prof. Eldar Saljic

Twenty-five years after the terrorist attacks against the United States on September 11, 2001, sufficient historical and academic distance now exists to assess their true significance more comprehensively. It is clear today that 9/11 was not merely one of the deadliest terrorist attacks of the modern era. It represented a strategic shock that transformed the international system, the concept of national security, and the way states understand threats, sovereignty, the use of force, and the relationship between security and individual liberty.

September 11 as a Transformation of the Security Paradigm

One of the most important consequences of September 11 was the collapse of the assumption that strategic threats of global significance must necessarily originate from states. A relatively small transnational terrorist network demonstrated that a non-state actor, without sovereign territory, a conventional military, or the traditional instruments of state power, could generate consequences comparable to those of major geopolitical crises.

This fundamentally changed the traditional understanding of power asymmetry. Asymmetry in capabilities no longer necessarily meant asymmetry in strategic effects. Al-Qaeda was incapable of defeating the United States militarily, but it was capable of provoking American and international responses that profoundly transformed global politics.

The consequences were far-reaching: the war in Afghanistan, the intervention in Iraq, the global “War on Terror,” the expansion of counterterrorism legislation, the strengthening of intelligence services, the transformation of border and aviation security, intensified monitoring of financial flows, the development of biometric systems, and the expansion of communications surveillance. At the same time, previously relatively separate functions of the military, police, intelligence services, civil protection, and homeland security structures increasingly became integrated within broader national security systems.

One lesson that has clearly been learned is that contemporary security can no longer be organized through isolated institutions. Modern security requires intelligence fusion, whole-of-government and, increasingly, whole-of-society approaches, together with intensive international cooperation.

From Military Victory to the Problem of Strategic Victory

The post-9/11 period also demonstrated the limitations of military power.

The United States and its allies demonstrated an extraordinary capacity to defeat adversaries militarily. However, Afghanistan and Iraq showed that tactical and operational superiority does not automatically guarantee the desired political outcome. In other words, winning the war is not the same as winning the peace.

This is one of the fundamental lessons of the past twenty-five years. Military force can destroy training camps, command structures, and the physical infrastructure of terrorist organizations. It can eliminate leadership figures and significantly reduce operational capabilities. Yet military force alone cannot eliminate the political, social, and ideological conditions from which violent extremism emerges.

“This reveals one of the central paradoxes of the post-9/11 era: the world has become significantly more capable of fighting terrorists, but it has not become proportionally more capable of preventing terrorism from emerging.”

From Al-Qaeda to an Adaptive Ecosystem of Extremism

Terrorism has not disappeared. It has transformed.

From the relatively hierarchical structures associated with Al-Qaeda, the international community moved into an era characterized by ISIS, its regional affiliates, decentralized cells, lone-actor terrorism, digital propaganda, online radicalization, and transnational networks combining extremist ideology, criminal activity, technology, and global communication platforms.

Therefore, in 2026 it is increasingly appropriate to speak of an adaptive ecosystem of violent extremism rather than focusing exclusively on individual terrorist organizations.

The experience of ISIS is particularly instructive. Its territorial “caliphate” was destroyed, but its ideology, networks, and regional affiliates did not disappear. This confirmed an important strategic reality: an organization can be destroyed while the narrative that produced and sustained it can survive.

Did September 11 Produce a “Clash of Civilizations”?

Twenty-five years later, particular caution is required when applying Samuel Huntington’s “clash of civilizations” thesis to September 11 and its aftermath.

There was no homogeneous confrontation between “the West and Islam,” nor between “Islam and the West.” However, a highly dangerous perception of such a confrontation emerged.

Terrorist organizations deliberately sought to construct a binary world divided between “us” and “them.” The strategic problem arises when states, political elites, or societies themselves begin to accept even part of this interpretation.

Wars, civilian casualties, Abu Ghraib, Guantanamo, and controversial counterterrorism measures were subsequently incorporated into extremist propaganda. At the same time, terrorist attacks in European cities contributed to fear, Islamophobia, anti-immigration sentiment, and political polarization.

This can create a spiral of reciprocal radicalization:

terrorism → fear → excessive response → perception of injustice → radicalization → further terrorism.

However, this should not be interpreted as a war between civilizations. Analytically, it is far more accurate to understand the confrontation as one between extremist and inclusive interpretations of political and social identity—divisions that exist within different civilizations and societies themselves.

“The greatest strategic victory of terrorism, therefore, cannot be measured only by the number of casualties it produces. It occurs when a terrorist attack succeeds in persuading societies to perceive an entire religion, culture, or community as an enemy.”

Have We Fought Terrorism—or the Causes of Terrorism?

This remains one of the most important unresolved questions after twenty-five years.

The international community has invested enormous resources in counterterrorism, but considerably less political energy in the prevention of violent extremism.

The first approach asks:

How do we identify and stop a terrorist?

The second asks a far more difficult question:

How do we prevent a potential terrorist from becoming radicalized and recruited in the first place?

There is no single universal cause of terrorism. Neither poverty, religion, education, nor political dissatisfaction alone produces terrorism. Radicalization generally results from a complex interaction between political marginalization, perceptions of injustice and humiliation, state repression, weak institutions, lack of economic and social prospects, war, state collapse, identity crises, and extremist ideologies that provide existing frustrations with an enemy and a political meaning.

Counterterrorism, therefore, cannot be exclusively a security policy. In the long term, it must incorporate the rule of law, legitimate institutions, education, economic opportunities, conflict resolution, the integration of marginalized communities, and the development of trust between citizens and the state.

An Unlearned Lesson: An Excessive Response Can Become Part of the Problem

One of the most sensitive lessons of the past twenty-five years concerns the possibility that the response to terrorism itself may generate new security problems.

If military intervention eliminates an immediate adversary but leaves behind an institutional vacuum, political instability, and widespread social dissatisfaction, it may create conditions for a new generation of violent extremism. The experience of Iraq demonstrates particularly clearly how inseparable the military and political dimensions of strategy are.

Every use of force must therefore answer a fundamental question:

What is the ultimate political objective?

Without a clear answer, tactical victory may ultimately produce strategic defeat.

Terrorism as a Communication and Cognitive Strategy

Another important lesson of September 11 is that terrorism cannot be understood solely through the physical violence it produces.

“Terrorism is a communication strategy based on violence.”

Its logic is based on using relatively limited physical means to generate disproportionately large psychological, political, and strategic effects. The September 11 attacks did not merely produce devastating human casualties; they transformed U.S. foreign policy, NATO strategy, national legislation, aviation security, intelligence structures, state budgets, and international relations.

Today, this dimension is even more significant because of social media, algorithmic amplification, artificial intelligence, and deepfake technologies. Terrorist actors no longer need to control traditional media. It may be sufficient to produce content that the digital information ecosystem can rapidly amplify and distribute.

Future counterterrorism strategies will therefore increasingly have to incorporate both information security and cognitive security.

The Paradox of Technological Superiority

Twenty-five years after September 11, states possess capabilities that in 2001 would have appeared almost futuristic: artificial intelligence, biometrics, satellite surveillance, sophisticated SIGINT analysis, automated processing of enormous quantities of data, and advanced systems for monitoring financial transactions.

Yet more data does not automatically produce more knowledge.

The contemporary intelligence challenge is increasingly shifting from the question “Do we have the information?” to “Can we identify the relevant information among billions of other data points?”

At the same time, no algorithm can independently resolve a civil war, political repression, corruption, social marginalization, or the erosion of public trust in institutions.

This represents a central paradox of contemporary security: we have never possessed greater technological capabilities to identify a terrorist, yet technology alone cannot eliminate the political and social conditions that facilitate radicalization.

From the “War on Terror” to Resilient Security

Perhaps the most important conceptual transformation to emerge from the past twenty-five years should be a shift from the pursuit of absolute prevention toward the concept of resilience.

No state can guarantee absolute security. Attempting to eliminate every possible risk could require levels of surveillance and control that would ultimately threaten the very freedoms the state seeks to protect.

For this reason, a contemporary security model must integrate:

prevention + protection + response + recovery + resilience.

A serious state should no longer ask only, “How can we prevent the next attack?” It must also ask: “If an attack nevertheless occurs, how can we prevent it from achieving its strategic objective and paralyzing the state and society?”

Conclusion: What Have We Learned in Twenty-Five Years?

Twenty-five years after September 11, the world is unquestionably more capable in security terms. Intelligence cooperation is more developed, critical infrastructure protection is more sophisticated, terrorist financing is more closely monitored, and states possess technological capabilities that were unimaginable at the beginning of the century.

Yet the fundamental problem has not disappeared.

“A terrorist organization can be defeated militarily. Terrorism as a social and political phenomenon cannot be bombed out of existence.”

Perhaps the most important distinction twenty-five years after the attacks is therefore this:

“During the first twenty-five years after September 11, we primarily learned how to fight terrorists. During the next twenty-five years, we will have to learn much more seriously how to prevent the emergence of environments in which terrorism can become a possible and attractive political option.”

The most successful counterterrorism operation of the future may therefore not be the one in which a terrorist is identified and eliminated. It may be the one in which a potential terrorist is never radicalized or recruited in the first place.

This requires a transition from predominantly reactive security toward preventive, integrated, and resilient security.

That is perhaps the enduring legacy of September 11, 2001. The attacks taught us that a small group of determined non-state actors can generate a global strategic shock. A quarter of a century later, however, we are still learning the more difficult lesson: long-term security is built not only through the capacity of the state to destroy a threat, but through the capacity of society to prevent the political, economic, social, and ideological conditions in which that threat emerges, reproduces itself, and acquires legitimacy.