Damascus, Syria—Medics treat the wounded in a field hospital in this city’s Douma neighborhood on December 13, after unidentified warplanes and surface-to-surface missiles fired by the Syrian army pummeled the neighborhood, the Syrian Observatory for Human Rights said. Douma is controlled by rebel groups battling the regime of President Bashar al-Assad. World leaders recently met in New York to discuss a peace plan that includes a two-year road map for ending the Syrian war, but differences remain, notably over whether Assad should step down.