That is insane.  There was no evidence Syria used chemical weapons last time either.  There is no way  the contents of bombs can be determined from high altitude photos.  Last time we blew up this air base, no chemical weapons were released.  That means we were wrong.  There were no chemical weapons there.  The only way to tell is with ground inspections, which only the UN can do.  So then why are we pretending?  It is illegal for the US to do anything.  Only the UN has any authority to act.