Leader: There is no good reason for our troops to remain in Afghanistan

The longer we stay in Afghanistan, the worse things will become.

The murder of 16 Afghan civilians by a rogue US soldier, in a house-to-house rampage across two villages just 500 metres from a US base in Kan­dahar Province, has led to much soul-searching. The dead included nine children and three women. A Pentagon spokesman described the 11 March shootings as a deplorable but "isolated" incident. They were not. In 2010, a group of US soldiers killed three Afghan civilians "for sport" and posed for pictures with the corpses; in January this year, a video emerged of US marines urinating on the bodies of dead Afghans.

We cannot ignore such crimes. On page 11, Frank Ledwidge, a former military intelligence officer and author of the acclaimed book Losing Small Wars, argues that the soldier accused in the most recent case "must take personal responsibility for his actions". The rest of us, he adds, "must reflect on our own willingness to send young men and women into wars such as this, time after time".

Why are we still in Afghanistan? Does anyone believe in the cause? The inconvenient truth is that most al-Qaeda fighters fled Afghanistan for the Khyber Pakhtunkhwa Province in Pakistan long ago. US officials estimate that there are fewer than 100 al-Qaeda fighters left inside Afghanistan; the Pentagon has conceded that the last time US troops killed an al-Qaeda fighter in the country was in April 2011.

Whether or not the US-led invasion of Afghanistan was justified following the terrorist attacks of 11 September 2001 is irrelevant now; few imagined Nato forces would still be fighting the Taliban more than a decade later in an intractable conflict that has dragged on twice as long as the Second World War.

The New Statesman has repeatedly called for a full withdrawal of British forces from the killing fields of Helmand. In August 2009, in a leader, we called on the previous Labour government to "set a date for withdrawal from Afghanistan. Our military presence is part of the problem, not the solution." We pointed out then that our heavy-handed military presence had become a recruiting sergeant, both for the anti-infidel Taliban insurgency and for al-Qaeda sympathisers in the UK. Since then, 208 British troops have died in Afghanistan, the killing of six soldiers in a roadside explosion on 6 March taking the death toll to 404 - more than twice as many as were killed in Iraq.

What of the blighted civilians of Afghanistan, so often forgotten? Tens of thousands of innocent Afghans have been killed since 2001; a recent UN study claimed that the number of civilian casualties had risen for the fifth year in a row.

Our Afghan misadventure has been a humanitarian and political disaster. And yet, writing in a joint editorial in the Washington Post of 13 March to coincide with David Cam­eron's visit to the US, the Prime Minister and President Barack Obama said that Afghanistan "remains a difficult mission. We honour the profound sacrifices of our forces, and in their name we'll carry on the mission."

This is wilful blindness. Soldiers will continue to kill and be killed; the UK's humiliating pull-out is merely being postponed. The year 2014 has been agreed as an end date for military operations but, as the Conservative MP Rory Stewart, one of the west's shrewdest observers of Afghanistan, wrote in the London Evening Standard on 12 March: "It is only a deadline: we are not obliged to stay till the last day."

The western allies could once have negotiated with the Taliban from a position of strength. That time is long past. The violence and bloodshed will continue, whether we stay or go. However, as Stewart wrote: "The longer we stay, the worse things will become."