IF THE Taliban were not so busy fighting the rival Islamic State jihadis who began operating in Afghanistan early this year, they might now be within reach of overthrowing the Afghan government that the Western powers left behind when they pulled out most of their troops last year. Even with
Gwynne Dyer: Taliban the lesser of two evils
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The 19th-century British army and the 20th-century Russian army could both have told them: it has always been easy to invade Afghanistan, but it has always been hard for foreign troops to stay there more than a couple of years.
And having made those mistakes, it was another mistake to pull almost all the foreign troops out before the Afghan government's army was up to holding the Taliban off. If, indeed, it can ever be brought up to that level. The parlous state of the Afghan National Army and the sheer fecklessness of President Ashraf Ghani's government was highlighted by last weekend's desperate plea by Helmand's deputy governor Mohammad Jan Rasulyar for supplies and reinforcements for the troops holding Sangin.
It's not just that the army had neglected the plight of those soldiers. It's the fact that Rasulyar had to resort to posting his plea on Facebook to get the government's attention.
Part of the problem is that the government and the army high command are profoundly corrupt. For example, up to a quarter of the army's troops are "ghost soldiers" who only exist on paper so that officers can draw their pay.
The worse problem is that President Ghani, a former senior official at the World Bank, only won last year's election by massive fraud.
Conflicts with the aggrieved losers have left the government paralysed: 20 months after the election, there is still not even a permanent defence minister.
Moreover, Ghani believes a decisive military victory over the Taliban is impossible. This is probably correct - but he is therefore committed to cultivating close ties with Pakistan in the hope that Inter-Services Intelligence (ISI), the Pakistani equivalent of the CIA, will deliver the Taliban to the table for peace talks. (Most Afghans believe that ISI controls the Taliban.) But Ghani is wrong on two counts.
The Taliban have no reason to agree to a power-sharing peace settlement, since they can still hope for an outright military victory. And Pakistan doesn't really control the Taliban, although it gives them a safe haven and can manipulate them to a limited extent.
The Afghan army would be collapsing a good deal faster if so much of the Taliban's attention was not focused on fighting off the challenge from Islamic State (it has killed at least a thousand IS fighters this year).
But the Taliban still managed to seize the city of Kunduz in the north for a week in September, and now Sangin in the southwest is going.
We are seeing the usual short-term responses in the West.
President Obama has halted the withdrawal of most of the remaining 9800 US troops in the country (which was scheduled for the end of this year), and Britain has ordered 10 of the 450 troops it still has in Afghanistan back to Sangin.
But that won't make much difference, and there is no chance whatsoever that the Nato countries will build their troop strength in Afghanistan back up to the level - around 140,000 - where it was five years ago.
The Afghans are on their own now, and they will be lucky if they end up back under the rule of the Taliban rather than in the clutches of Islamic State.
-Gwynne Dyer is an independent journalist whose articles are published in 45 countries.