THE occupation of Afghanistan after 9/11 had a clear purpose: to remove the Taliban from power and stop the country being a base for Al-Qaeda. That was achieved quite quickly.

Now there is a lack of political clarity about why we are still there and considerable alarm about the death and maiming of British soldiers. This has caused some people to say that British troops should immediately leave Afghanistan.

The great danger of withdrawing now is that the Taliban and Al-Qaeda could return to fill the vacuum. There would then also be a bigger threat to Pakistan, where violent Islamic fundamentalists are already trying to seize control of a country with nuclear bombs.

It may be popular to give up in Afghanistan, but I think it would be a mistake.

Improvements brought about in Afghanistan since 2001 are an effort to create a country that we can safely leave to its own devices. Nation-building is a painstaking and difficult process.

There is a military dimension, but it also involves diplomacy and economic assistance. Our soldiers are involved in this process, along with civilian staff.

Afghanistan is not a self-contained war with a straightforward objective, like the Falklands.

It is a process, in that way more like Bosnia, or even Northern Ireland. We are not going to create a perfect Western-style liberal democracy. What we can try and do is create the conditions which make the country reasonably stable and safe.

Afghanistan is dangerous - we see that nearly every day with British soldiers being killed - but doing nothing in Afghanistan is dangerous too.

Defending our security and our values remains a justifiable and vital objective.

We need a clear strategy - from the Americans, other NATO allies and our own Government - but I fear that if we turn our backs now we may come to regret it.