The Bashar Assad regime in Syria has used poison gas ("chemical weapons" is the nicey nicey name for it) on their own people. Some time ago, Obama made a threat to do unspecified bad things to Assad if he used poison gas. Well, Assad went ahead and gassed his rebels. Now Obama is under pressure to make good on his idle threats. New secretary of state, old Viet Nam war veteran, "Swift Boat John" Kerry is beating the drum for action against Assad.
Syria has a nasty dictator, Bashar Assad, under attack from Al Quada. We don't own Assad a thing, and Al Quada is Al Quada. Getting mixed up in the Syrian civil war is a choice between two repulsive sides. Most Americans are would just as soon let the two sides fight it out, without absorbing any more US casualties in Mid East peace keeping actions.
Now, that Assad has crossed Obama's red line, Obama is finding that he doesn't have political support for military action in Syria.
This is something that most parents learn early. If you make a threat to the kids, you gotta make good on it. Obama has two daughters, he shoulda learned by now. Or maybe he is a slow learner.