The BBC begins a week of in-depth coverage of Afghanistan by asking its World Affairs editor, John Simpson, to consider if the Afghan government and the West can win the war against the Taleban.
Nato soldiers have been killed patrolling the roads from Kabul to Jalalabad
The Taleban have new confidence and new tactics, and their campaign against the government and its Nato backers has been increasingly successful since the beginning of this year.
In the east of the country, around Jalalabad, suicide bombings have become such frequent occurrences that the road from there to Kabul is now known as "the Baghdad road".
I have been coming to Jalalabad since 1989, but for the first time in my experience we needed a police escort to drive around there. In the countryside near the town, they urged us not to get out of our vehicle when we stopped, despite the intense heat.
"There are spies everywhere," the police explained.
The police themselves are a major target for the Taleban and al-Qaeda guerrillas who operate here now.
Outside the main police headquarters in the town, a senior policeman ran out and ordered us to stop filming in case our presence attracted the attentions of a suicide bomber.
There have been several attacks there, and an unexploded rocket is still lodged in a tree in front of the building.
Until the end of last year, Jalalabad was relatively quiet. Now it is becoming a battleground.
Along part of the length of the so-called "Baghdad Road", local people point out the places where American soldiers fired at passers-by a few weeks ago, after an attempted suicide bombing.
The soldiers claimed they had come under small-arms fire from the side of the road.
The local authorities later apologised and paid compensation for the deaths.
As a result of this and other incidents in this part of the country, Nato and US troops are often regarded with dislike and distrust.
The Taleban's tactics are designed to make people feel there is no safety anywhere.
Last week, just north of Kabul in an area which has always been a stronghold of support for the government and for the Northern Alliance which swept the Taleban from power in November 2001, the Taleban staged a fierce and concerted attack on a pro-government village.
Just south of Kabul, in Logar province, two schools have been attacked in the past few days, and schoolgirls murdered or injured. The Taleban are particularly opposed to the education of women.
At the hospital where one of the schoolteachers and her pupils were being treated, they begged us not to film them for fear of the consequences.
And the capital itself experienced on Sunday its worst bombing since the fall of the Taleban in 2005, when more than 30 people were killed in an attack on a police bus.
For several years after the Taleban were chased out of power, they seemed to be finished. Girls went back to the schools which the Taleban had closed down, women's groups started up and women appeared on television as newsreaders.
Now a new campaign of murder against prominent women has begun.
With Nato troops mostly tied up in the southern part of the country, the Afghan police and army are finding it harder to operate elsewhere. New recruits, new weapons and new tactics are coming in to help the Taleban from outside.
Civilians in Afghanistan increasingly distrust Nato troops
Especially from Iraq. Al-Qaeda, the Taleban's close ally, is redirecting some of its forces here.
The new al-Qaeda commander in Afghanistan, Mustafa bin Yazid, has himself had combat experience in Iraq, and is thought to be behind the new tactic of suicide-bombing; something that was relatively rare in Afghanistan until recently.
But the Taleban are not winning all the battles. I spoke to a senior Taleban figure who has just defected to the government in Kabul after falling out with the overall Taleban leader, Mullah Omar.
He maintained that many Taleban leaders like himself are hostile to al-Qaeda, and are looking for some third way between the government with its Nato allies and the foreign extremists led by bin Yazid.
But he agreed the Taleban were proving increasingly successful against the government, and confirmed that their strategy was to surround Kabul and eventually capture it.
While Nato forces are in the country, that will not happen. But so far neither Nato nor the government of President Karzai seems to know how to counter the resurgent Taleban.