The 9/11 attacks were the first major historical event of the 21st century, and one of the most horrific.
The huge terrorist attack, which was broadcast live to billions of viewers around the world, was enacted in the collective consciousness as a reality-changing and world-changing event.
A group of 19 Islamist terrorists, in the service of a mysterious terrorist organization that few in the world knew, managed to strike at the heart of the world's great superpower and shatter some of its great symbols of power.
In four coordinated attacks, using passenger planes hijacked as "flying bombs," al-Qaeda terrorists killed nearly 3,000 U.S. civilians, leaving the world stunned.
The 9/11 attacks were not only the deadliest attack on U.S. soil, but also a wake-up call for an international fight against terrorism. Very entangled unknowingly.
The war between Western values and those of radical Islam and Islamic terrorism took place in almost every corner of the globe, defining more than anything the political landscape of the new century.
In contrast to the inter-bloc struggle and the fear of a nuclear world war that characterized the second half of the 20th century, the fear of al-Qaeda's ruthless terror captured the imagination of the 21st century.
Al Qaeda itself has operated in different countries under different names, and its charismatic leader - Osama bin Laden - was eliminated by the US in 2011. But the brutal methods and distorted vision outlined by bin Laden and his terrorists are still a candle to his successors, and a nightmare that haunts the world. The whole free.
