It's worth keeping track of what the neocons are saying about Afghanistan. They think that they have Barack Obama on the back foot on this one, with Iraq "proving" that a troop increase can have powerful effects in taming an insurgency and with the US (thanks to 7 years of neglect) facing some very awkward choices when ideally the choices would be either scale up massively or just go home. But anyway, one critical issue in both Afghanistan and Iraq is whether the USA (or similar power) can ever really "win" a war fought via a domestic proxy. Here's Max Boot --
The worst thing the Obama administration could do is throw up its hands in despair and claim we can’t win in Afghanistan because of [Hamid] Karzai’s problems. In fact, every counterinsurgency effort in history has faced a problem of governmental legitimacy; if the government were generally accepted as legitimate and efficient, there would be no insurgency to begin with. Enhancing governmental credibility is a tough task but by no means a mission impossible — we’ve helped achieve that outcome in countries as varied as Greece, the Philippines, and El Salvador.
So let's take Greece which is perhaps the least well-known example in the US. The Wikipedia article on the period on question is excellent. There are a few things to note.
First, this was a civil war in which the US picked a side. The Cold War made things relatively simple since they could mapped into 2 sides: Communist and not-Communist. Do Iraq and Afghanistan have 2-sided civil wars?
Second, what eventually did in the Greek Communists? A falling out between Tito and Stalin. They needed Tito for the logistical support but Stalin for the ideology, and when there was a row, most of the leadership chose the latter. Which was a huge mistake. Yugoslavia was a lot closer.
Third, Greece does resemble Afghanistan in one important respect. The locals had seen off a hated foreign occupier (Nazi Germany and the USSR respectively) pretty much on their own. Having someone else waltz in at the end to declare themselves in charge didn't go down very well with the people who had stuck it out at home. Hence the legitimacy problems to which Boot obliquely refers.
And finally, if we are looking at outcomes following US interventions to boost a local client, Greece is close to the best case scenario. It's now a rich country in the European Union and NATO, with a significant foot in eastern Mediterranean/Adriatic politics and good (if complex) relations with most of its southeastern European neighbours. But that's 50 years after its civil war ended. In between there's been military coups, dictatorships, the partition of Cyprus, a terrorism problem that never really went away, mass emigration, street riots, and poisonous domestic politics.
If the American people are to be told the truth about what a prolonged Afghan adventure would involve, shouldn't this decades-long scenario be part of the sales pitch?