A very good discussion of the different contributions to the Sunni forces which are uncorrectly labled as ISIL is found on "Sic Semper Tyrannis", the host W.P. Lang, with obviously deep knowledge of this subject, makes very good contributions.

It is IMHO worth not only to read the posts but also the discussion, Lang, Habakuk and other can explain various aspects of US and UK decision making.