Twenty-five years after 9/11: how the lessons of the attacks are still being learnt

Twenty-five years after the September 11, 2001 attacks, the worst terrorist act in history continues to reshape global security, intelligence practices, and foreign policy in ways that are still being understood.

The attacks, which killed 2,977 people in New York, Washington and Pennsylvania, prompted the United States and its allies to launch the longest wars in American history — in Afghanistan and Iraq — fundamentally reordering global politics for a generation.

Intelligence agencies were overhauled, surveillance expanded dramatically, and the concept of preventive action moved from legal theory to operational doctrine. Yet with hindsight, analysts note that many of the warning signs had been visible, and coordination failures between agencies allowed the plot to proceed.

Across the world, memorials were held on Friday marking the anniversary. In Washington DC, President Trump attended a ceremony at the Pentagon; in New York, the names of all 2,977 victims were read at Ground Zero, accompanied by a drone light show recreating the Twin Towers in the night sky.

Families of British victims gathered at a London event featuring a video tribute from Prime Minister Andy Burnham. Zelensky, who was speaking at the YES forum in Kyiv, expressed Ukraine's condolences to the United States.