No matter what you do, they cant fire you. You can just keep on coming back.
And now we have completely lost the war. The only way giving a city (or two) to the former enemy makes any sense is as a first step toward a rather immediate and total withdrawal. Anything else is now based on total fantasy. The "insurgents" have defeated the US Marines, because for whatever reason, at the end of the day, it was the Marines who withdrew. They wont forget it and they wont let anyone else either. And they now have a city (or two) to use as a base for spreading their insurgency. What kind of imperial power gives whole cities away to their opponents? One that is on the way out.