Dr. Mohammed Arif helps treat a wounded patient at a field hospital in Kobani, Syria. Most of the clinics in this besieged Syrian border town are now in ruins. Only one still stands, its location kept secret lest it be targeted. Jake Simkin/AP hide caption

itoggle caption Jake Simkin/AP

A member of the Saudi border guards mans a machine gun at the border with Iraq in July. Since the so-called Islamic State launched its offensive this summer in Iraq, Saudi Arabia has sent thousands of troops to the region. Faisal Nasser/Reuters/Landov hide caption

itoggle caption Faisal Nasser/Reuters/Landov

Peter Kassig, who changed his first name to Abdul-Rahman when he converted to Islam, is shown with a truck filled with aid supplies for Syrian refugees. Courtesy of Kassig family hide caption

itoggle caption Courtesy of Kassig family

Displaced demonstrators from the minority Yazidi sect demonstrate outside the United Nations offices in Irbil, Iraq, on Aug. 4 in support of those held captive by the self-proclaimed Islamic State. Azad Lashkari/Reuters/Landov hide caption

itoggle caption Azad Lashkari/Reuters/Landov

Fighters from the Islamic State group parade down a main road in the northern city of Mosul, Iraq. A Yazidi woman nicknamed Dudu tells the story of how she was kidnapped by ISIS along with her sisters and other women, to be sold and married off. AP Photo hide caption

itoggle caption AP Photo

Lt. Gen. William C. Mayville Jr., Joint Staff Director of Operations, speaks about airstrikes in Syria during a briefing at the Pentagon yesterday. Brendan Smialowski/AFP/Getty Images hide caption

itoggle caption Brendan Smialowski/AFP/Getty Images

Yemeni soldiers hold up their weapons at an area seized from al-Qaida in the southeastern province of Shabwa, Yemen, on May 8. President Obama said Wednesday that U.S. strategy against the so-called Islamic State would be similar to how it targeted militants in Yemen and Somalia. Yemen's Defense Ministry/AP hide caption

itoggle caption Yemen's Defense Ministry/AP

A flag of the Islamic State — aka ISIS, aka ISIL — is seen on the other side of a bridge at the front line of fighting between Kurdish Pesh Merga fighters and Islamist militants in Rashad, Iraq, on Thursday. The group is referred to differently depending on who's talking about it. JM Lopez/AFP/Getty Images hide caption

itoggle caption JM Lopez/AFP/Getty Images

President Obama addresses the nation from Cross Hall in the White House on Wednesday. Opening a new military front in the Middle East, Obama authorized U.S. airstrikes inside Syria for the first time, along with expanded strikes in Iraq as part of a broad mission to root out violent Islamic State militants. Saul Loeb/AP hide caption

itoggle caption Saul Loeb/AP

A U.S. military plane lands Aug. 11 on the U.S. Navy aircraft carrier USS George H.W. Bush in the Persian Gulf. U.S. public support of airstrikes against Islamic militants jumped sharply, according to a new poll, as President Obama prepares a strategy. Hasan Jamali/AP hide caption

itoggle caption Hasan Jamali/AP

Freelance journalist Steven Sotloff is seen during a work trip inside Al-Fateh Mosque in Manama, Bahrain, on Oct. 26, 2010. The Islamic State group released a video this week that showed a militant beheading the American journalist. Mazen Mahdi/EPA/Landov hide caption

itoggle caption Mazen Mahdi/EPA/Landov

British Prime Minister David Cameron told the House of Commons on Monday that he wants to give police the power to seize the passports of Islamist fighters bound for Iraq and Syria. PA Photos /Landov hide caption

itoggle caption PA Photos /Landov

This image, posted on a militant website, shows an Islamic State fighter waving a flag from a captured government fighter jet in Raqqa, Syria. The group is well-funded and has gained territory over the past few months; that's raised some concerns in America, although experts say the organization is largely focused on regional goals. AP hide caption

itoggle caption AP

This image is from the Facebook page of the now-renamed 3 Thirty Three Downtown. The project in West Palm Beach, Fla., was previously called ISIS Downtown. 3 Thirty Three Downtown/Facebook hide caption

itoggle caption 3 Thirty Three Downtown/Facebook

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