Leading article: An honourable withdrawal

British troops should not have been in Iraq in the first place. Their presence is now making the situation worse. Meanwhile, the British Army has a mission in Afghanistan that is morally justified, winnable and under-resourced. The time has come to stop pretending and announce that the vast majority of the 7,000 British soldiers in Iraq will leave within a year.

General Sir Richard Dannatt, the Chief of the General Staff, has broken the spell of Tony Blair's make-believe. It is some time since the Prime Minister has pretended that things are getting better in Iraq, but he has continued to hold the line that immediate withdrawal would only make matters worse. And that has probably been true for most of the time since the invasion. It almost certainly remains true of the American presence in Baghdad and central Iraq. But Sir Richard says, in effect, that whatever his troops in the south are achieving is outweighed by the simple provocative fact of their uninvited presence in the country.

As Patrick Cockburn sets out in his new book, most Iraqis were glad to see the back of Saddam Hussein, but they felt humiliated that it took the Americans to depose him. They were bound to become increasingly keen to see the back of coalition forces in turn. The Independent on Sunday has been describing that reality for some time; now the head of the British Army endorses it publicly. That changes the political reality.

We have reached the point where our political leaders can and should say honestly that British forces have done all they can do in Iraq. They continue to do the important job of training the Iraqi army in the desert outside Basra. But that task is nearly finished, and the fitful attempts to impose order on the warring local militias are either counterproductive or ineffective.

That does not mean, it should be stressed, that this newspaper wants all foreign troops out of Iraq in the next few months. The Americans have to stay for a while longer. Bad though the situation currently is in central Iraq, that is where the front lines of an all-out civil war would lie. The presence of US troops may not be much of a deterrent to carnage, but in their absence the bloodletting is likely to get worse.

It may be that a British presence should be maintained, at Balkan levels of hundreds rather than thousands, to continue training the Iraqi army. It would not help the Iraqis if the British withdrawal were portrayed as a victory for insurgents, or if it undermined the Americans' task. As we report today, a detailed plan already exists for a phased British withdrawal. If it has been delayed until after the US mid-term elections on 2 November, that would be the worst reason for putting off what has to be done.

The shape of what has to be done has suddenly become very much clearer. Sir Richard deserves to be congratulated for speaking the truth. He said, in effect, that the Army does not believe in its mission in Iraq. The soldiers do not believe that they have a strong moral right to be there. And they do not believe that they have military objectives that are achievable - certainly not with the resources available to them.

The general has been criticised for disagreeing publicly with ministers. True, the Government, drawing its authority from the House of Commons, normally sets military policy, and the generals lead the armed forces in implementing it. But that takes us back to the folly of the decision to join the invasion of Iraq in the first place. Because the case for war was so flawed, it never commanded the secure support of the British people. The nation needs to be sure why it is risking its troops; the families of soldiers need to know why their loved ones are dying; and the soldiers themselves need to know why it might be them next.

Those conditions have never been fully satisfied. For three years, it has been possible to maintain a pragmatic humanitarian justification for the British military presence in Iraq. But, as Sir Richard says: "We need to keep on thinking about time, because time is against us, because time is money, time is particularly soldiers and soldiers' lives, and we can't go on forever."

The time has come to devote the main military effort of this nation to a war that the vast majority of the country and its soldiers can support, in Afghanistan, and to leave Iraq to the Americans. It is not too late to try to put right the failure of the international community in following through the toppling of the Taliban.

Pulling out of Iraq would not be an admission of defeat, nor even an admission of error (although errors there have most certainly been). It would be a pragmatic calculation of the interests of the Iraqi people, and it would be a sensible rebalancing of Britain's military contribution to the security of this country and the world.