![Pentagon with American Flag draped over the west wall.](https://webarchive.library.unt.edu/eot2008/20090117201853im_/http://www.fbi.gov/homeimag/flagpent1.jpg)
They
were the most lethal terrorist attacks in history, taking
the lives of 3,000 Americans and international citizens and
ultimately leading to far-reaching changes in anti-terror
approaches and operations in the U.S. and around the globe.
Our
ensuing investigation of the attacks of 9/11/01—code-named
“PENTTBOM”—was our largest investigation
ever. At the peak of the case, more than half our agents
worked to identify the hijackers and their sponsors and,
with other agencies, to head off any possible future attacks.
We followed more than half-a-million investigative leads,
including several hundred thousand tips from the public.
The attack and crash sites also represented the largest
crime scenes in FBI history.
For more information: