U.N. envoy Staffan de Mistura arrived in Damascus on Saturday for talks aimed at ending the fighting in Syria. The diplomat hopes to persuade both sides in the conflict to stop fighting in Aleppo through a series of locally negotiated truces that would allow humanitarian aid to be taken in — part of a "very complicated but very important effort" to make progress in Syria. De Mistura said in mid-February that the Syrian government had agreed to suspend airstrikes and artillery...