The Principle of Calculated Risk
The former administration left Syria in sinking condition. It is unclear whether the ship can still be saved, but the cries of the victims are so heart-rending and their number so huge that the pressure to row back the lifeboats to save them even at the risk of swamping is difficult to resist. In December of 2016 Jamie Dettmer at VOA wrote: "Assad's survival now looks almost certain, thanks to Russian and Iranian support for the Syrian regime on the battlefield."
Russia's influence inside Syria appeared so great at one point Israeli prime minister Netanyahu flew to Moscow to seek Putin's reassurances that Hezbollah would not be allowed to take up positions along the Yarmouk river-Shebaa line across the Golan. Perhaps Assad's greatest stroke of luck was the abortive Turkish 'coup' which took Ankara out of the fight. Yezid Sayigh writes for Carnegie that "the abortive coup of July 2016 ... has prompted Turkish President Recep Tayyip Erdogan to defuse foreign policy crises in order to focus on challenges within his country’s borders. This means abandoning the effort to remove Assad from power."
Together these developments have forced Syrian rebel groups to perversely gather under the Jihadi flag to survive against a resurgent Assad. "After years of byzantine internal disputes, Syria’s armed rebels are suddenly gathering into large, centrally directed organizations of the kind they always needed to threaten President Bashar al-Assad’s authoritarian regime. But rather than a winning move, these last-minute unifications look more like the prelude to ultimate defeat. The balance of power in opposition-held northern Syria has now swung sharply in favor of hardline Islamists and an internationally targeted jihadi group, whose growing influence is more likely to drive Western states over to Assad’s side than to topple him."
The reality is that knocking out ISIS only begins to address the problem of battlefield full of villains. The Boss fight still lies ahead. As Aaron Lund wrote "an aggressive intervention of Gulf money, Turkish military aid, and U.S. drone strikes might be able to shift things around, but that is by no means certain and even less likely to be tested." But now there's a chance. With Russia and Iran weakenened by falling oil prices and Putin beset by internal opponents they no longer seem so invincible.
If anything the renewed calls for action against Assad -- and by implication Russia -- are a backhanded compliment to Donald Trump. But compliments don't win conflicts. As if to remind the civilian world of what a campaign in Syria involves Agence France Presse reported that "The United States has expanded a runway at a northern Syria air base to accommodate the large C-17 military plane needed to help with logistics for the push to retake the ISIS stronghold of Raqqa ... The huge military air freighter will play an essential role in supplying the Syrian Democratic Forces as they mount an offensive to retake the city, ISIS's last big stronghold in Syria." Amateurs it is said, talk strategy but professionals talk logistics. The logistics of a fight against Assad will be substantial.