Secretary of Defense Chuck Hagel (left) and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey during a Pentagon briefing on Thursday. Hagel said Islamic State militants in Iraq and Syria posed a threat "beyond anything we've seen." Yuri Gripas/Reuters/Landov hide caption

itoggle caption Yuri Gripas/Reuters/Landov

A picture taken with a smart phone shows Syrian refugees queuing at one of the many UNHCR (United Nations Refugee Agency) registration centers in Lebanon. At the same time that civil wars and the Ebola outbreak are plaguing countries in Africa, Syrian and Iraqi refugees are seeking help from agencies. Joseph Eid/AFP/Getty Images hide caption

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Smoke rises during airstrikes targeting Islamic State militants at the Mosul Dam outside Mosul, Iraq, on Monday. Kurdish forces say they have retaken the dam, but the militants insist they still have control. Khalid Mohammed/AP hide caption

itoggle caption Khalid Mohammed/AP

Lincoln, Neb., is home to a sizable community of Iraqi Yazidis — including Ismaeil Khalaf, shown here in his home watching the latest news about the Yazidi crisis in Iraq. Lincoln Yazidis petitioned for U.S. intervention to prevent the genocide of their friends and family. Nati Harnik/AP hide caption

itoggle caption Nati Harnik/AP

Displaced people from the minority Yazidi sect walk toward the Syrian border on the outskirts of Sinjar mountain on Monday. A U.S. assessment team says far fewer refugees are stranded on Mount Sinjar than previously thought. Reuters/Landov hide caption

itoggle caption Reuters/Landov

Iraqi children from the Yazidi community wave to Kurdish peshmerga forces near Dohuk, the Kurdish region of autonomous Kurdistan in Iraq. The children fled with their families from their hometown, which was attacked by Sunni militants from the Islamic State. Ahmad Al-Rubaye/AFP/Getty Images hide caption

itoggle caption Ahmad Al-Rubaye/AFP/Getty Images