Twenty-five years ago on Thursday, nineteen hijackers seized four commercial airliners, killing 2,983 people in New York, Washington and Pennsylvania.
What began as an attack on the United States rapidly became a turning point for the entire international system, reshaping security, law, and diplomacy far beyond American borders.
A Worldwide Security Overhaul
Within weeks, the UN Security Council adopted Resolution 1373, compelling all member states to criminalise terrorism financing, tighten border controls, and share intelligence, a mandate that pushed countries from Europe to Southeast Asia to rewrite their counterterrorism laws.
Airport security protocols drawn up in the attacks' aftermath, including passenger screening standards set by the International Civil Aviation Organization, were adopted globally, standardising checks, watchlists, and cockpit security across airlines far from American soil.
NATO And The Reordering Of Alliances
For the first time in its history, NATO invoked Article 5, its collective-defence clause, treating the attacks on the US as an attack on all member states. This drew European and other allied forces into the war in Afghanistan, entangling dozens of countries in a conflict that stretched two decades.
The subsequent invasion of Iraq in 2003 further split international opinion, strained transatlantic relations, and destabilised the Middle East in ways that contributed to the later rise of ISIS and prolonged civil conflict in Syria and Iraq.
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New Laws, New Fears, Everywhere
Governments worldwide followed Washington's lead in expanding surveillance and detention powers.
Countries including the UK, India, and several EU states introduced or toughened anti-terror legislation in the years that followed, from India's Prevention of Terrorism Act to Britain's expanded detention laws after the 2005 London bombings.
Muslim communities across the West and beyond reported a sustained rise in discrimination, while migration and asylum policies tightened in many countries citing security concerns.
A Global Toll That Continues
The wars launched in the attacks' wake killed an estimated hundreds of thousands of people and displaced millions across Afghanistan, Iraq and neighbouring states, effects still visible in refugee flows today.
At Friday's commemoration in Lower Manhattan, organisers added a seventh moment of silence — now permanent — honouring those who have died from illnesses linked to the attacks and their aftermath, a reminder that the human cost of that day has never fully stopped accumulating, in America or abroad.
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