Syria can be a key to turning the Russians

Anne-Marie Slaughter:

...

The problem is that if Assad continues to believe that he can do anything to his people except kill them with chemicals, he will exterminate his opponents, slaughtering everyone he captures and punishing entire communities, just as his father, Hafez al-Assad, massacred the residents of Hama in 1982. He has demonstrated repeatedly that he is cut from the same ruthless cloth....
A US strike against the Syrian government now would change the entire dynamic. It would either force the regime back to the negotiating table with a genuine intention of reaching a settlement, or at least make it clear that Assad will not have a free hand in re-establishing his rule.
...

The US, together with as many countries as will cooperate, could use force to eliminate Syria’s fixed-wing aircraft as a first step toward enforcing Resolution 2139. “Aerial bombardment” would still likely continue via helicopter, but such a strike would announce immediately that the game has changed. After the strike, the US, France, and Britain should ask for the Security Council’s approval of the action taken, as they did after NATO’s intervention in Kosovo in 1999. 

...

There is much more.

She proposes to change the dynamic with Russia by knocking out their ally Syria.  Her proposal makes some sense but it requires leadership which has been in short supply with the Obama administration.