Secretary of State John Kerry said yesterday that Syria's use of chemical weapons is "undeniable," a "moral obscenity" and a violation of international law. He added, "The President will be making an informed decision about how to respond... President Obama believes there must be accountability." By drawing a "red line," the Obama Administration has set the stage for some kind of military action. Advocates say it's a matter of "credibility" to make good on a threat -- with Iran and other adversaries closely watching. But what could make a difference to Bashar al-Assad, without drawing the US into yet another implacable civil war? Have so-called "limited actions" really worked in the past? How much will be tolerated by a war-weary American public?