File:September 2016- Ground Zero Flag.jpg

English: This year marks the 15th anniversary of the September 11, 2001 terrorist attacks. 9/11 was the most lethal terrorist attack in history, taking the lives of 3,000 Americans and international citizens and ultimately leading to far-reaching changes in anti-terror approaches and operation in the U.S. and around the globe. Galvanized by the unprecedented terrorist attack, the FBI responded in an unprecedented fashion. Within minutes, officials at FBI Headquarters in Washington, D.C. activated the Strategic Incident Operations Center. By the end of the day, the FBI had established command posts for each of the three crash sites.

In addition to assisting emergency response efforts, the FBI began its PENTTBOM investigation, short for Pennsylvania, Pentagon, and Twin Towers Bombing. The PENTTBOM investigation was the largest investigation ever conducted by the FBI. Thousands of agents across the nation interviewed witnesses and sources; they followed more than half-a-million investigative leads worldwide, including several thousand tips from the public, in order to determine what had happened, who did it, and how future acts could be prevented. At the peak of the case, more than half of the Bureau’s agents worked with other agencies to identify the hijackers and their sponsors. Within hours, the FBI was able to start identifying the 19 terrorists responsible.

Director Robert S. Mueller, III broke with routine and based the massive investigation out of the FBI Headquarters instead of a field office. The investigation was coordinated out of a basement office, where dozens of agents would toil for several years to build a case against those responsible, including Zacarias Moussaoui, who pleaded guilty in April 2005 to six charges related to his participation in the 9/11 conspiracy.

This month’s #ArtifactoftheMonth is the American flag from Ground Zero in New York City. On this 15th anniversary, we remember those who lost their lives in these attacks. In particular, we honor the memories of those who gave their lives to save others, including Special Agent Lenny Hatton and former Special Agent in Charge John P. O’Neill.

For more information on the PENTTBOM investigation: www.fbi.gov/history/famous-cases/911-investigation.