The Big Question: Why are British troops back in Afghanistan five years after the war?

What are British troops doing in Afghanistan?

About 3,300 British troops have been sent to the southern Afghan province of Helmand for what the Government says will be a three-year, £1bn deployment. Britain is stepping into the breach, with Canada and Holland, as the biggest partners in a new Nato-led mission that is seen as the last chance to turn around an increasingly dire situation where a resurgent Taliban, local warlords and a powerful drugs mafia have supplanted such government control as existed in many areas.

Isn't Afghanistan supposed to be a success story?

There have been great achievements since 2001. Presidential and parliamentary elections were adjudged successful; six million children including many girls banned from education by the Taliban are back at school, 4.5 million refugees have returned home, while economic growth has been strong. But for two years there have also been signs that beneath the veneer of progress in the big cities, large parts of the rest of the country are sliding back towards the anarchy that afflicted Afghanistan during the 1990s and gave rise to the Taliban.

To complicate matters Afghanistan's only significant export is heroin. This illicit $2.7bn (£1.46bn) industry warps the entire economy, fuelling corruption, bankrolling the criminal mafia and, increasingly, the Taliban, and giving a huge number of the population a vested interest in maintaining the instability.

What is the British plan to turn this around?

The British are looking to the experience gained from decades of fighting counter-insurgencies around the globe. In Helmand this means a four-stage strategy based on the premise that if they are offered security and economic opportunity, the majority will swing behind the Afghan government and their foreign backers. British forces will first seek to establish a safe zone in Helmand and destroy any Taliban within that. Once security is established the British Department for International Development plan to deluge the area with millions of pounds worth of "quick impact" projects designed to produce rapid improvement in the lives of the local people. Simultaneously, the military will hope to train local security forces to begin to take over from them and begin longer term infrastructural development with other non-government organisations moving in. The final stage sees British troops moving to new areas, creating a series of widening circles of peace and prosperity that will eventually join up.

What problems do they face?

The British commanders aren't pretending it will be easy, or quick, and the numbers of soldiers involved are desperately economic for the control of an area 250 miles by 250 miles. Nor do they enjoy the sort of luxury in equipment, particularly transport helicopters, that their American predecessors enjoyed. That makes the job more difficult and more dangerous.

As the death of a British soldier on Sunday showed, the Taliban remain a force in the south. They have succeeded in killing ever larger numbers of foreign soldiers since 2001. With the adoption of tactics perfected by insurgents in Iraq, specifically the use of suicide bombers and massive roadside bombs, they killed more than a hundred foreign soldiers last year.

As well as fighting the Taliban, British soldiers will have to win the battle for hearts and minds. This will be far from simple in one of the most conservative, opaque and dizzyingly complex tribal societies on earth. And the British will be hindered as much as helped by their supposed Afghan allies. The corrupt Afghan National Police are regarded as little more than bandits with uniforms by much of the populace while many provincial and central government officials they will work with are linked to the drugs mafia, local warlords, the Taliban or all three.

Which way will the locals swing?

The majority of the Pashtuns in the south are not deeply committed to the Taliban's ideology, which is propagated through madrasa religious schools which arelargely on the Pakistani side of the border.

It is, though, a profoundly conservative tribal society with a strong streak of xenophobia running through it, and central government has never had significant influence in the region. Gun-wielding foreign soldiers will be tolerated for a while, but only if they are bringing clear tangible benefits in terms of security and economic benefits. This, the American forces failed to do, particularly during the early days after the fall of the Taliban when they alienated much public opinion by aggressive search operations that were anathema to the Pashtun social code; though they are doing a better job in the eastern areas that they control these days.

British commanders believe that a more sensitive approach to local custom, combined with the prospect of peace and imminent prosperity will do the trick. The Taliban's increasingly active propaganda machine seeks to counter that by portraying the British as infidels who have come to pillage Afghanistan for their own ends, strip the impoverished opium farmer of his livelihood and impose immoral Western values. It also stresses the historical enmity Britain has with Afghanistan after three imperial invasion attempts; Afghans are great students of history and all know they beat the British every time.

What about drugs?

With drugs the mainstay of the Helmand economy (it single-handedly supplies 20 per cent of the world's heroin) British commanders cannot afford to alienate the populace by being associated with poppy eradication. However, it is equally clear that there are increasingly close ties between the Taliban and the drugs mafia, while drug money is at the root of many of the central government's problems. If the British are successful in seeing off the Taliban and introducing some sort of economic stability the drug smugglers and then finally the poppy farmers will be on the target list; not least because Britain is officially supposed to head the international effort against narcotics in Afghanistan.

For the small poppy farmer, the British hope that economic alternatives and peace will be a worthwhile alternative to a life of insecurity and poppy cultivation. However, with poppy a miracle crop that combines great reliability with a return 10 times that of any alternative, that calculation is far from certain.

We are in, so when do we get out?

The British deployment is set to last three years. However, few believe that the situation can be stabilised in that time. British officers talk more in terms of a decade to effect irreversible change for the better while entirely solving Afghanistan's opium production problem will probably take two decades.

Will Britain succeed in Helmand province?

Yes

* Their plan stresses peace and economic prosperity, the two things Afghans say they want most.

* British forces bring a wealth of experience in subtle counter-insurgency work and a joined-up civil military approach.

* By not targeting poppy cultivation the British effort maximises the chances of winning widespread popular backing.

No...

* The British force in Helmand is too small for the job it is being asked to do and badly under-equipped.

* Britain faces a population terrified of Taliban retribution and suspicious of Western motives.

* British troops must rely on allies who are unreliable at best, and in some cases a major part of the problem they have been sent to solve.