IT'S beyond satire. US Defence Secretary Robert Gates, telling the what he had learned during his long tenure under presidents Bush and Obama, explained that “I will always be an advocate in terms of wars of necessity. I am just much more cautious on wars of choice.” Gosh, Bob, does that mean you wouldn't invade Iraq next time?

Afghanistan, by contrast, was a 'war of necessity' in Gates's terms: official Washington believed that further bad things like 9/11 might happen to the United States if US troops didn't go to Afghanistan to root out the Al Qaeda terrorists (mostly Arabs) who had been given bases there by the country's Taliban leadership. It wasn't a very subtle strategy, but it was certainly driven by perceived US national interest.

Which was the point being made by President Hamid Karzai, the man whom the United States put in power after the 2001 invasion: “[The Americans] are here for their own purposes, for their own goals, and they're using our soil for that.”

Well, of course. The only other possible explanation for their presence would be that Washington had sent half a million young Americans to Afghanistan over the past 10 years in some quixotic quest to raise the Afghan standard of living and the status of Afghan women. That's ridiculous. Obviously, the motive was perceived US national interest.

So how to explain the furiously emotional response of Karl Eikenberry, the US ambassador to Afghanistan? Speaking at Herat University, he raged: “When Americans ... hear themselves described as occupiers, told that they are only here to advance their own interest ... they are filled with confusion and grow weary of our effort here.”

“Mothers and fathers of fallen soldiers, spouses of soldiers who have lost arms and legs — they ask themselves about the meaning of their loved one's sacrifice. When I hear some of your leaders call us occupiers, I cannot look these mourning parents, spouses and children in the eye and give them a comforting reply.”

Karl, they won't be very comforted if you tell them that their loved ones died for Afghanistan. Tell them that they died defending America. Except, of course, that it may not have been a very useful way of defending America.

All the Al Qaeda camps were quickly smashed after 9/11, and by the end of 2001 Osama bin Laden had escaped across the border into Pakistan, where he remained until his death last month. Most of the surviving Al Qaeda cadres also fled to Pakistan, and US intelligence says that there are only a couple of hundred left in Afghanistan.

So why have American troops been in Afghanistan for almost 10 years? To keep the Taliban from power, they say, but it's unlikely that the Taliban leadership ever knew about Al Qaeda's plans for 9/11. Why would they support an action that was bound to provoke a US invasion and drive them from power? Why would Bin Laden risk letting them know about the attack in advance? The US has probably been barking up the wrong tree for a long time.

Now the Taliban are back in force, and the war is all but lost. The US may think it is about 'terrorism' and Al Qaeda, but for Afghans it is just a continuation of the civil war that had already been raging for almost a decade before the US invasion. The Taliban, almost entirely drawn from the Pakhtun ethnic group, captured Kabul in 1996, but they never managed to conquer the other, smaller ethnic groups in northern Afghanistan.

The United States stumbled into this civil war under the delusion that it was fighting Islamist terrorists, but in fact it has simply ended up on the side of the Tajiks, Uzbeks and Hazaras. So long as the US forces remain, the Taliban can plausibly claim that they are fighting a jihad against the infidels, but once the Americans leave the war will probably return to its basic ethnic character. In the end, some deal that shares out the spoils among the various ethnic groups will be done: that is the Afghan political style. The Taliban will get a big share, but they won't sweep the board.

But in the meantime, President Barack Obama has promised to start withdrawing US troops from Afghanistan next month, and that will be very tricky. Few Americans know much about Afghan realities, and they have been fed a steady diet of patriotic misinformation about the place for a decade.