An academic reflection on the 25th anniversary of the terrorist attacks on the United States, examining the transformation of security, the limits of military power, the evolution of violent extremism, technological challenges and the need for preventive and resilient security.

Twenty-five years after September 11, remembrance must be joined by strategic honesty: counterterrorism achieved much, but Afghanistan demonstrated that military superiority, without sustainable political strategy and local resilience, cannot by itself secure a lasting outcome.