ISIS came to the attention of most Americans this summer, when it overran the Iraqi city of Mosul in a lightning advance. But the terrorist organization has been around much longer than a few months -- and appeared in security and news reports well before it became a household name.
Asked about ISIS in an interview that aired Sunday on “60 Minutes” on CBS, President Barack Obama suggested the ISIS threat was graver than initially thought, saying that “our head of the intelligence community, Jim Clapper, has acknowledged that I think they underestimated what had been taking place in Syria.”
The White House press secretary, Josh Earnest, echoed the president, saying Monday that Obama “absolutely” has confidence in the intelligence services and that “nobody predicted the speed and pace” of ISIS’ advance and seizure of territory.
But Syria’s deputy foreign minister, Faisal Mekdad, told NBC News on Monday that the United States should not have been surprised by ISIS, adding that Syria has been warning about it for three years.
One thing is not in doubt: the organization has been growing for years, since its origins within al Qaeda. Here is a timeline, drawn from NBC News reporting and other news accounts, of how we came to know about ISIS:
October 2006: Jihadist groups within the Iraqi insurgency, including some affiliated with al Qaeda in Iraq, establish the Islamic State of Iraq, and vow in a video recording to plant “the flag of the state of Islam,” according to documents released by WikiLeaks.
Late 2006-early 2007: The Islamic State of Iraq’s leader, Abu Omar al-Baghdadi — not the same Baghdadi as today’s ISIS leader — claims growing support among Sunnis in Iraq and says that the organization has set up courts. The Islamic State seeks to distinguish itself from al Qaeda in Iraq, according to a monitoring group.
March 2007: The Islamic State of Iraq is blamed for burning dozens of houses outside Baghdad, and victims tell The New York Times that the attackers demanded money, weapons and oaths of support.
2009-2012: The Islamic State of Iraq takes credit for outbreaks of violence across Iraq, killing hundreds of people and beginning to overpower Iraqi security forces just as the U.S. hands over more authority, and finally full authority, to them.
May 2010: The Islamic State of Iraq names a new leader: A commander known as Abu Bakr al-Baghdadi, who has a low profile and spent an unremarkable few years in American custody before being turned over to Iraqi authorities in 2009.
July 2012: Baghdadi announces a campaign called “Breaking the Walls,” designed to secure the release of prisoners and reclaim lost territory in Iraq. It is a yearlong offensive including car bombs, mostly aimed to kill Shiite civilians, and prison breaks.
April 2013: The Islamic State of Iraq announces that it has merged with the Nusra Front, a jihadist group fighting President Bashar Assad in Syria and affiliated with al Qaeda, and takes the name Islamic State of Iraq and the Levant, also known as ISIL or ISIS.
May 2013: Some Nusra leaders tell news outlets that Nusra has split, some agreeing with the merger and others not. Among the Nusra fighters loyal to the new merged operation are three who carried out a triple public execution in Raqqa, Syria.
July 2013: ISIS has begun launching attacks almost every day against Iraqi citizens and security forces. It claims responsibility for a prison break in which more than 500 inmates escape, including some ISIS commanders.
July 2013-January 2014: Activists report that ISIS is gradually seizing control of smaller cities in northern Syria. In January, it takes control of Raqqa, its first capture of a major city.
February 2014: Al Qaeda, unable to resolve a dispute over Nusra, cuts ties with ISIS. An al Qaeda statement characterizes ISIS as too stubborn and unconcerned with teamwork, according to The Washington Post.
June 2014: ISIS launches its biggest offensive yet and captures vast expanses of both Iraq and Syria, including Mosul, the second-largest city in Iraq, and Saddam Hussein’s hometown, Tikrit. ISIS leaders announce that they have established a caliphate.
Aug. 7: President Barack Obama announces that he has authorized airstrikes against ISIS in Iraq to roll back the militants and break a mountaintop siege in which ISIS has trapped thousands of people.
Aug. 19: ISIS releases a video depicting the beheading of James Foley, a hostage American journalist, and warning of more to come if Obama does not call off the airstrikes.
Sept. 2: ISIS releases a video showing the beheading of a second American journalist who had been held hostage, Steven Sotloff, and threatening a British hostage if the airstrikes continue.
Sept. 10: Obama, in a prime-time address, vows to “degrade and ultimately destroy” ISIS and authorizes additional airstrikes in Syria. Obama vows to build an international coalition to help.
Sept. 13: ISIS beheads a third Western hostage, David Haines, a British aid worker.
Sept. 22: The United States, joined by five Arab allies, launches its first airstrikes in Syria. Later in the week, Britain, Belgium and Denmark join the coalition, which the administration says now numbers more than 40 countries.
Emmanuelle Saliba of NBC News contributed to this report.