New york: Twenty-five years after the September 11, 2001, attacks, their consequences continue to shape global politics, security policy, and conflicts from the Middle East to South Asia. The attacks, carried out by 19 al-Qaeda hijackers using four passenger planes, killed 2,977 people at the World Trade Center in New York, the Pentagon near Washington, and near Shanksville, Pennsylvania.
According to Anadolu Agency, the attacks triggered the US-led 'war on terror,' NATO's first use of its collective defense clause, the invasion of Afghanistan, the creation of new US security institutions, the Guantanamo detention system, the Iraq war, the rise of new militant movements, and two decades later, the Taliban's return to power. The global fallout of the post-9/11 era extended far beyond initial battlegrounds, causing an estimated more than 900,000 direct deaths, including over 400,000 civilians, and leading the US federal government to spend or obligate over $8 trillion through 2021.
Beyond direct combat, an estimated 3.6 to 3.8 million people have died indirectly from war-related destruction, disease, malnutrition, and infrastructure collapse across conflict zones in Afghanistan, Pakistan, Iraq, Syria, and Yemen. The 9/11 attacks and their aftermath have left a lasting legacy, reshaping international relations and security measures worldwide.
The post-9/11 era saw significant milestones, including the invocation of NATO's Article 5 for the first time, the Authorization for Use of Military Force resolution by the US Congress, and the subsequent invasion of Afghanistan. The USA Patriot Act was signed into law, expanding law enforcement and intelligence powers, while the establishment of the Department of Homeland Security marked a significant reorganization of US domestic governance.
The US-led invasion of Iraq in 2003, justified by claims of weapons of mass destruction, resulted in years of insurgency and instability, becoming one of the most divisive consequences of the post-9/11 era. The Madrid train bombings in 2004 and London transport bombings in 2005 underscored the global reach of terrorism, reshaping security debates across Europe.
The death of Osama bin Laden in 2011 marked a significant chapter in the US pursuit of al-Qaeda's leadership, although the wider conflict persisted with the rise of ISIS/Daesh and the declaration of a 'caliphate' in 2014. The US and Taliban signed the Doha deal in 2020, setting terms for the withdrawal of forces from Afghanistan, culminating in the Taliban's return to Kabul in 2021 and the US completing its withdrawal.
The 25th anniversary of 9/11 arrives with the physical legacy of the attacks still present in New York, Washington, and Pennsylvania, and the political legacy visible across the world. The conflicts and policies initiated after 9/11 have formally ended or transformed, but their impacts endure, shaping surveillance powers, airport security, detention and torture debates, state stability, displaced populations, and a global counterterrorism architecture that continues to evolve.