In a dialogue with Anthony Cordesman at The Cipher Brief he puts his finger on the nub of the problem in Afghanistan:
Now, within this, there is no sort of national solution. We are talking different areas, different branches of ethnic groups like the Pashtuns and other ethnic groups, particularly in the north, and sectarian differences. The country’s economy differs sharply according to urban area, and particularly, according to water and the size of agricultural areas. Part of the problem is that governance is so different in different parts that when you talk about finding a common solution, it doesn’t really work that way. That’s been part of the problem – you are attempting to somehow talk about one-size-fits-all with respect to military forces, local forces, police, economic reform, and governance reform, and in many cases, you simply don’t have the resources to do it.
No president wants to be the one who allowed Afghanistan to return to its status as the world’s largest training camp for terrorists but no president wants to admit the truth—that there is no Afghanistan to unite—and the only way to maintain the fiction is for us to remain there indefinitely.
So we remain there indefinitely and don’t say that’s what we’re going to do, neither pacifying the country nor accomplishing anything except domestic political goals.
We’ve been in Somalia for 24 years, and we’re still fighting the locals.
By the way, the Cordesman quote reads like a description of the US.