@hawkeye10,
hawk--there is a way of thinking that would say that the "red line" speech as good as guarantees that there will be a gas attack.
The Arab and Islamic world would see Assad as weak if he didn't respond to such threats from the US. And if there was no gas attack his enemies, and he will have a goodly number, would have said exactly that.
Which raises two possibilities which I don't suppose I need explain to you.