The USA is claiming that Assad's troops were braced for gas attacks three days prior to August 21st - do we believe what the USA is saying?
The USA knew that Saddam used chemical weapons against Iran's military in the early 80's and gave that usage blessing by actively providing Saddam with targeting data, and turning a blind eye to the results. When Saddam then gassed civilians in Halabja in 1988 the CIA spread disinformation suggesting that Iranians were responsible for the atrocity, rather than be forced to contend with the cognitive dissonance of their erstwhile ally being a mass murderer.
So, the USA has form, on record, revealed by it's own archives published after 30 years, for deliberately lying about the perpetrators of chemical attacks, and it has form for tolerating chemical weapons when their usage by third parties is aligned with the US national interests, early 80's Iran being a greater evil than early 80's Iraq.
Suppose it's true Assad is responsible for the chemical weapons attack on the 21st August. Why is bombing the right response? Why only respond to chemical weapons attacks? Today, we see the disgusting results of Napalm being dropped on a Syrian school by the Assad forces, with children described by doctors as 'the walking dead', arriving with >50% burns to field hospitals, to shiver in agony while they wait to die of inevitable infection and fluid loss. Chemical weapons are nothing special when it comes to causing horrible death.
A half-cocked approach is not the answer. The world needs to come together and impose peace here, not some unilateral action. George Bush was a blundering ape, so war is his mode of operation. Obama is a statesman, so then he should step up to the plate of convincing the Russians to come on board with an authentic peace plan. He needs to make an accord with Iran and provide a way to reach peace in Syria.