US: ready to give up
Syria: hey Russia come help

Your a pretty good reporter but I think you lack some serious analysis on Syria. The US was in a pickle so to speak. With Assad forces busy fighting the opposition that the US was backing (whether under questionable means is another story) ISIS was rapidly advancing into Syria. The US couldn't see taking out Assad if there was even a chance the vacuum of power would have fell to ISIS, it would have been just another mess like Iraq had become. The US couldn't just say hey now we are going to back both sides so the only other alternatives was to have Russia come into the picture. This is why there was let up on sanctions in place at the time, the deal was for Russia to come in and get a grip on ISIS, that's exactly what they did. There are horror stories told about the atrocities that Russia used to gain the upper hand, places where they took prisoners and tortured them to give up locations of ISIS leadership, actually it worked much better than if the US had tried to do it because unlike the US were people get all queasy about this stuff Russian people don't question those in authority. As strange as a reality that that may be that the US didn't want to take Assad out that is why they didn't, that is why they don't give further involved in a all out war, this tit for tat will continue until there's a consensus on who will control the power vacuum if and when Assad were to leave, to not guarantee such would leave Syria looking quite a bit like the mess created in Iraq.