According to CNN:
The U.S. is investigating what it believes are “credible” reports that ISIS fighters used mustard agent in an attack against Kurdish Peshmerga this week, causing several of them to fall ill, U.S. officials working in at least three separate parts of the Obama administration said Thursday.
ISIS couldn’t possibly augment its reputation for cruelty and barbarism or do much to demonstrate further its willingness to violate the rules of war. Chemical warfare has long been considered the “forbidden weapon,” and use of such weapons as mustard gas has been outlawed by treaty since 1933. The grim surprise, if there is any, is that it took ISIS so long to get around to it.
