This is a developing illustration of how the governing class "pulls the wool" over the eyes of the people in the US. Corporate media will be very instrumental in this deceit by covering the phony withdrawal as if it were real.
Using private forces is a backdoor way of continuing a substantial US presence under the cover of "diplomatic security." The kind of paramilitary force that Obama and Clinton are trying to build in Iraq is, in large part, a bi-product of the monstrous colonial fortress the US calls its embassy in Baghdad and other facilities the US will maintain throughout Iraq after the "withdrawal."