Operation Moshtarak, which means "together" in the Dari language, is poised to begin. There is more than usual significance in the name. Nato commanders have been at pains to make it clear that Afghan forces, alongside Western troops, will play a prominent role in the operation to clear Taliban insurgents from the town of Marjah, the largest community in Helmand province under Taliban control.

General Stanley McChrystal, the top Nato commander in Afghanistan, has said he wants the military operation, which will be one of the most significant in the country since the fall of the Taliban in 2001, to send a very clear signal to the country that the Afghan government is expanding control over its territory.

There is logic to this. The operation is part of the new Nato strategy, driven by General McChrystal, of building up the Afghan military presence and establishing security in large civilian centres. And the fact that Nato has been broadcasting this operation for weeks (forgoing the advantage of surprise) and has not sought to prevent Taliban fighters from leaving Marjah fits with the other strategic goal of splitting the less-committed insurgents off from the hardcore.

This strategy is certainly smarter than the previous one of sporadic engagements with the Taliban, followed by a retreat to isolated bases. But it is likely to come at a price, as the Defence Secretary, Bob Ainsworth, stressed at the weekend. Two more British soldiers have been killed by a bomb in Helmand, taking the military death toll in Afghanistan to that of the 1982 Falklands campaign. Before this operation – involving some 4,000 British troops – is over, there are likely to be more casualties.

The risk of civilian deaths is significant too. Thousands of residents of Marjah area have been departing in haste after Nato airdropped warning leaflets. But by no means all have fled, as the International Committee of the Red Cross made clear yesterday. The flipside of Nato forces taking control of a major civilian centre is that it unavoidably puts civilian lives in the path of danger.

Even more daunting is the fact that the McChrystal plan is not certain to work. The Nato commander is aiming for something that has never been achieved before in Afghanistan. Throughout history, insurgencies have always come out on top over foreign forces. And some foreign forces had even more troops than this one. The whole strategy is also reliant on the Afghan government, which has revealed itself as incompetent and corrupt. Last week a district administrator in north western Afghanistan was arrested, accused of selling government supplies for private gain and passing sensitive military intelligence to militants.

As General McChrystal admits himself, the success of the operation will depend, in large part, on convincing civilians that the government in Kabul will be better for them than the control of the Taliban. The test for Operation Moshtarak is not in the initial assault, but what happens in Marjah afterwards.

The clock is ticking too. When President Obama approved the deployment of 30,000 more American troops last year, he laid down a tight timetable for the demonstration of progress. That will be hard to meet. Yet the McChrystal strategy should at least be given an opportunity to prove itself. Marjah looks like being its first major – and possibly decisive – test.