What this does is to signal that further use of WMD runs the risk of waking the dragon, i.e. drawing the U.S. into the conflict. Being the "dragon" may make a lot of folks uncomfortable, since it goes against the USA's vision of itself as a city on the hill and a step removed from everything beyond its coasts...but a lesson from history is, never be the side with the weaker military. We're #1 there by a considerable margin, which for better or worse means that we're the dragon that no one wants to face, and will continue to be...and can say, which is how Jerry Pournelle put it: "The message is clear: You had six air bases, Now you have five. Do you care to try for four? Or fewer?."
I note that Pournelle and others on the further right are of the opinion that it made no sense for Assad to use chemical weapons when his star is on the ascendant in the civil war, and what is more likely is this was a "false flag" by ISIS or the opposition to try and draw outside powers into a fight they're losing. At this point, I think that's supposition without any hard facts to back it up, and I'm willing to give the NSA/CIA/etc. the benefit of the doubt that the evidence indicated that the chemicals came from an attack out of that airbase until otherwise indicated.
Crossposted from http://tagryn.dreamwidth.org/237501.html where there are comments. Comment wherever you prefer; anonymous comments are allowed on DW only