Syria "may be a Humpty Dumpty that can't be put back together again," retired four-star general and former CIA Director David Petraeus said in an interview aired Monday night amid a discussion about the regional complexities in the coalition fight against the Islamic State. […]

Earlier in the interview, Petraeus urged against keeping American boots on the ground as "not sustainable."

"I would not at this point," Petraeus said. "Again, you need to have a hold force that has legitimacy in the eyes of people that has to be Sunni Arab forces."

Asked whether it should be American forces, Petraeus said, "it should not be."