Free Syrian Army fighters run behind sandbags in Daraa Al-Mahata, in southern Syria, on Jan. 21. Many moderate rebels joined the uprising to fight against President Bashar Assad, but the U.S. plans to train them to fight the self-proclaimed Islamic State. Wsam Almokdad/Reuters/Landov hide caption

itoggle caption Wsam Almokdad/Reuters/Landov

Syrian President Bashar Assad, shown here in July, appeared to be in a tough position at the beginning of the year. But many analysts say his hold on power grew stronger over the course of 2014, due in part to the U.S. bombing campaign against the Islamic State. SANA/AP hide caption

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Syrian Foreign Minister Walid Moallem (left) at the peace talks in Montreux, Switzerland, on Wednesday. Gary Cameron /Reuters/Landov hide caption

itoggle caption Gary Cameron /Reuters/Landov

In the northern Syrian city of Aleppo last month, there was a class about how to protect against chemical weapons attacks. J.M. Lopez/AFP/Getty Images hide caption

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A convoy of U.N. vehicles with chemical weapons experts on board head out on Friday to do more work as the investigate allegations of chemical weapons use in near Damascus. Louai Beshara /AFP/Getty Images hide caption

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A Free Syrian Army fighter looks through the scope of his sniper rifle at an area controlled by forces loyal to President Bashar Assad in Aleppo. Reuters/Landov hide caption

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In Washington, D.C., this week, there have been demonstrations both in favor of and against a military strike on targets in Syria. Outside the White House on Monday, supporters of Syrian President Bashar Assad waved a Syrian flag with his face on it. Jewel Samad/AFP/Getty Images hide caption

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Vice President Joe Biden stands in front of his residence at the Naval Observatory in Washington, D.C., on Sunday, as President Obama arrives at a dinner Biden is hosting for Republican senators. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP

Sen. John McCain, R-Ariz., and Sen. Lindsey Graham, R-S.C., met with President Obama on Sunday at the White House. Jewel Samad /AFP/Getty Images hide caption

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Lindsay Graham, R-S.C., right, accompanied by Sen. John McCain, R-Ariz., speaks Monday following a White House meeting with President Obama. Both senators are calling for a tough military response against Syria. Pablo Martinez Monsivais/AP Photo hide caption

itoggle caption Pablo Martinez Monsivais/AP Photo