Islamic State of Iraq and Syria Islamic State of Iraq and Syria

A member of Iraq's elite counterterrorism service flashes the "V" for victory sign Tuesday in Ramadi, the capital of Iraq's Anbar province. Iraq's prime minister says the extremist group will be pushed out of Iraq in 2016. Ahmad Al-Rubaye/AFP/Getty Images hide caption

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Ahmad Al-Rubaye/AFP/Getty Images

After Ramadi, A Look At What's Next In The Fight Against ISIS

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This undated file image posted on a militant website on Jan. 14, 2014, shows fighters from the Islamic State of Iraq and the Levant (ISIL) marching in Raqqa, Syria. Uncredited/AP hide caption

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Uncredited/AP

The Psychology Of Radicalization: How Terrorist Groups Attract Young Followers

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"You've got to respect how this guy keeps on saying stuff he surely doesn't actually believe himself and KNOWS are impossible and unconstitutional to actually do," writes a reader of the Jakarta Post, after presidential candidate Donald Trump spoke of a ban on Muslims entering the U.S. Sean Rayford/Getty Images hide caption

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Sean Rayford/Getty Images

Federal Bureau of Investigation assistant director David Bowdich speaks during a news conference on Friday in San Bernardino, Calif. The FBI is officially investigating the attack carried out by Syed Farook and his wife Tashfeen Malik as an act of terrorism. Justin Sullivan/Getty Images hide caption

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Justin Sullivan/Getty Images

An image from the report "ISIS in America: From Retweets to Raqqa" shows (clockwise from top) a suspended Twitter user announcing their new account, and examples of other Twitter accounts that help spread extremist information online. Program on Extremism/George Washington University hide caption

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Program on Extremism/George Washington University

Anti-terror police detain a man identified as Ahmet Dahmani, an alleged ISIS member, in Antalya, Turkey, Saturday. One of three people arrested, Dahmani is accused of scouting locations for last week's terror attacks in Paris. IHLAS News Agency/EPA /LANDOV hide caption

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IHLAS News Agency/EPA /LANDOV

Municipal employees clean the exterior the Carillon cafe, one day after a terrorist attack hit Paris. ISIS has claimed responsibility for the deadly violence. Antoine Antoniol/Getty Images hide caption

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Antoine Antoniol/Getty Images

A U.S. drone aircraft used a Hellfire missile to hit a target that was believed to include Mohammed Emwazi, known as "Jihadi John," seen here in an image made from a militant video that has been verified by SITE Intel Group. AP hide caption

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AP