Questions about how and when a Syrian truce will be implemented deepened skepticism that the cease-fire will work, as Russian and Syrian warplanes on Friday sustained their relentless bombardment of rebel-held territory in the country. Syrian opposition groups cautiously welcomed the deal reached by world powers at a meeting in Munich on Thursday but said they were concerned that it allows Russia to continue its air campaign against the Islamic State and Jabhat al-Nusra terrorist groups — and perhaps also against moderate rebels. The deal marks the first attempt to bring about any kind of pause to the fighting since a U.N.-backed cease-fire in 2012 collapsed within hours, and world leaders expressed hope that this agreement would herald the beginning of an end to the nightmarish war. But […]