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

President Obama has been wary of open-ended military commitments in the Middle East. But the president, shown speaking in Estonia on Sept. 3, now appears likely to expand the current bombing campaign against the Islamic State. Saul Loeb/AFP/Getty Images hide caption

itoggle caption Saul Loeb/AFP/Getty Images

Smoke rises from the Beiji oil refinery during clashes between the Islamic State and Iraqi government forces in Beiji, northern Iraq, on July 30. The militants tried to take the refinery this summer, but government forces have held on. STR/EPA/Landov hide caption

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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

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A photo from March 2008 provided by the Hennepin County, Minn., Sheriff's Office shows Douglas McAuthur McCain, who was killed recently fighting alongside Islamic State militants in Syria. AP hide caption

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American Eric Harroun threatened Bashar Assad on Facebook and YouTube. He spent six weeks fighting with a rebel army, a journey that did not end well for him. ABC News/YouTube hide caption

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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

Syrians inspect a site hit by what they said were airstrikes carried out by President Bashar Assad in the Eastern Ghouta area on Aug. 3. Assad's forces continue to besiege the area near Damascus, which is still controlled by rebels. Badra Mamet/Reuters/Landov hide caption

itoggle caption Badra Mamet/Reuters/Landov

President Obama leaves after making a statement Wednesday about the killing of journalist James Foley in Syria. The president said the U.S. would continue to confront Islamic State extremists despite the brutal murder. Jacquelyn Martin/AP hide caption

itoggle caption Jacquelyn Martin/AP

Forces loyal to Syria's President Bashar Assad walk along a street in Mleiha, near the Damascus airport, during a tour organized by the Syrian government on Aug. 15. Omar Sanadiki/Reuters/Landov hide caption

itoggle caption Omar Sanadiki/Reuters/Landov