A member of the Islamic State of Iraq and the Levant urges Syrians in the city of Aleppo to fight against the Assad regime. This week, the militants apologized for beheading a commander from another anti-Assad group. Karam al-Masri/AFP/Getty Images hide caption

itoggle caption Karam al-Masri/AFP/Getty Images

A doctor vaccinates a child against polio at a health clinic in Damascus, Syria, on Nov. 6. To stop the disease from spreading beyond Syria, health officials plan to vaccinate 20 million children in the region. Youssef Badawi/EPA /LANDOV hide caption

itoggle caption Youssef Badawi/EPA /LANDOV

A Syrian fighter from the Islamist rebel group Jabhat al-Nusra inspects a resident's identification papers at a checkpoint in Aleppo on Oct. 26. Syria's Islamist fighters are generally better funded than their more moderate counterparts. Reuters /Landov hide caption

itoggle caption 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

itoggle caption J.M. Lopez/AFP/Getty Images

A photo released by the Syrian official news agency SANA Thursday shows an international expert working at a chemical weapons plant in Syria. Destroying the weapons safely may require them to be moved to another country, experts say. AP hide caption

itoggle caption AP

Children play at the Zaatari refugee camp in Jordan, where more than 120,000 Syrian refugees live. Roughly two-thirds are kids, many of whom have been traumatized by the violence in their homeland. Cassandra Nelson/Mercy Corps hide caption

itoggle caption Cassandra Nelson/Mercy Corps

Syrian opposition fighters sit on the front line in the city of Deir Ezzor on Oct. 13. Ongoing violence has ravaged the city since March 2011. AFP/Getty Images hide caption

itoggle caption AFP/Getty Images