David Petraeus' next tough assignment will be in the trenches of academia. The University of Southern California is announcing today that the retired general and former CIA director is joining the faculty to teach classes and mentor ROTC members. At USC, Petraeus will hold the title of Judge Widney Professor, which is named for the university's founder and is reserved for eminent teachers. Petraeus left the CIA in November after acknowledging an extramarital affair with his biographer, Paula Broadwell.