I was standing behind an old fashioned parapet made of mud brick and oil drums looking out across the lovely orchards of the Shomali valley at the Taleban positions opposite when the action of the day began.

The unmistakable insect-like hum of a jet gradually got louder and the Northern Alliance soldiers around me - just kids with guns for the most part - started pointing up into the sky. There it was, a tiny silver cross in the blue.

My cameraman focused on it and filmed it unleashing its single bomb. He followed the bomb's downward flight all the way to its target. Later we timed it. It took a full 26 seconds to hit the ground.

There was a boiling up of orange flame and thick grey smoke about two miles away across the valley, and the kids with guns let out a fierce shout. A Taleban tank had taken a direct hit.

It's not a good feeling to watch people being cremated alive, even from a distance, but you had to admire the extraordinary technical achievement that had brought this pilot several hundred miles from his base in Uzbekistan and allowed him to drop a bomb so smart that it could find its way to earth and hit a target smaller than a city bus absolutely dead on.

We'd just seen $20m of advanced technology in action.

But the soldiers weren't impressed - they were glad the tank was gone because it had been making a nuisance of itself, but this air strike wasn't quite what they'd been hoping for, nor was the rest of the afternoon's bombing as it unfolded.

The more time I spent with them the more I began to understand why they felt that way.

Standing behind my embrasure I watched as another billowing cloud went up over a Taleban position.

Deadly accuracy

And yet it all seemed so remote, so quiet, so safe. There was no possible threat to us, I thought.

These American bombs are so accurate they usually hit precisely what they're aiming at.

It may be different in a city where the Americans have sometimes bombed the wrong things. But out here on the front line, I've only heard of a couple of minor mistakes with no injuries.

It seems reasonable to assume that the Taleban on the other side of no-man's land feel rather the same. It isn't as if the bombing missions are frequent.

Twice or three times a day maximum, and always with this scalpel-like accuracy.

It's a bit like the old maxim about not worrying unless your name's on the bomb.

And it isn't as though everyone on the Taleban's side is a target.

I've been on the front line every day since the Americans began to bomb them, and it quickly became obvious that it was only the positions known to be occupied by Arab, Pakistani or Chechen volunteers that were being targeted. The ones manned by Afghans have been left alone.

The strategy is plain enough and it seems quite a sensible one at first sight. The Americans want the Afghans fighting for the Taleban to come over to the Northern Alliance side.

No defectors

But when I was invited to a meal by a senior Northern Alliance commander I know, I found there were several other leading commanders there, sitting cross-legged around the floor, eating his delicious bread and honey and yoghurt.

They explained to me gloomily that this strategy wasn't working at all. They had noticed absolutely no feelers whatever from would-be Taleban defectors since the American bombing began.

A week or so ago, I filmed my host in the trenches speaking by walkie-talkie to a particular friend of his who's fighting for the Taleban, trying to persuade him to change sides.

Now it seems the friend simply isn't interested. It's not that he's a religious extremist, he just thinks the Taleban are going to win this trial of strength with the Americans and he feels it would be a big mistake to leave them now.

Most of the commanders here fought the Russians in the 1980s. They remember how terrifying it was when the Soviet planes came over.

Russian pilots didn't care how many civilians they killed - they just let go their bombs in the general area of the target.

The superb, exquisitely accurate weapons which the Americans are using are meant for an altogether different and more advanced type of warfare.

In the rough, unsophisticated circumstances of Afghanistan, they just seem a bit feeble, a bit effete. So far, I have to say, the Americans may have been spending a lot of money but they haven't had much return on it.