It's Christmas Day, and I'm on the road from Herat to Kandahar to discover more about the resistance in the south of Afghanistan, and how the situation might be expected to develop through the new year. On the ten-hour blur of dust, discomfort and unfinished roads, we pass through the dasht-e margo (the 'desert of death'), adding to the sense of foreboding that any travel in the south usually inspires; banditry and robberies are common.

My third time in the country, conversant in Dari and Pashto (the two national languages), and a long-term follower of events in Afghanistan, I immediately notice a difference. Informal check-points have sprung up. Formal check-points are manned occasionally by black-masked troops, fearful of reprisal attacks for working with the government. Several times we are asked to get out of the car for a search; they're looking for suicide bombers. A small bribe (around 10 $-cents or so) bypasses this, thus completely negating the logic of the checkpoints. Welcome to Kandahar.

The heart of the original Taliban movement, it is a city almost exclusively dominated by Pashtuns, the tribal peoples of southern Afghanistan and border-land Pakistan, and recently the site of a number of suicide bombings, attacks and political assassinations. The Pashtuns have traditionally ruled the country. In 1747 Afghanistan - meaning 'land of the Afghans', itself an alternative word for Pashtun - was first created with its capital as Kandahar. Only later in the century was it moved north to Kabul, on account of tribal riots.

Pashtuns are a very proud people, unwilling to give control to others without invitation. It's a characteristic that gives rise to their reputation for fierce resistance to invaders. Whole empires have been broken in the south: the British fought three unsuccessful wars against the Afghans around the end of the nineteenth century, finally resorting to air bombing of Kabul and Jalalabad in 1919 which ended the war on their own terms. They left soon after. Over half a century later, the Russians also met their match in a decade-long struggle that eventually resulted in the collapse of the Soviet Union, not to mention millions killed, injured and made refugees.

Nowadays, the south and east are enveloped in an intractable conflict: Al-Qaeda and neo-Taliban forces are fighting a guerrilla war against the government and coalition soldiers (a broad grouping of the US and its allies) stationed here. Suicide bombings, previously unknown in Afghanistan, are increasingly common as a tactic against convoys. Similarly, IEDs (Improvised Explosive Devices) fashioned from landmines are used to target government and coalition forces. Decapitations are becoming more common. Kidnapping of foreigners happens less only because so few work in the south.

All this points to a migration of tactics from Iraq. Training manuals and videos originating there have been found both in Afghanistan and Pakistan. These detail how to make IEDs or the best way to decapitate prisoners. They're also used as recruitment tools, promising payments of some $2000 to the family of a suicide bomber, for instance, or $1250 to the killer of a coalition soldier. Over the summer, there was a flurry of reports - most notably a Newsweek interview - that Afghans had actually been taken to Iraq (to Ramadi, sometime capital of the insurgency there) for training. These allegations have resurfaced in a widely-syndicated Sunday Times article.

After further enquiry with Afghans, Non-Governmental Organisations (NGOs) and other security sources, I discovered that actually much of the south was 'no-go' territory for government/coalition troops, foreigners and non-locals. Much of this area is, in fact, under the control of Taliban forces. The main road linking Herat in the west to Kabul is relatively safe, barring banditry, suicide bombers and IEDs. Kandahar City itself is relatively stable, despite recent assassinations of moderate religious clerics and school teachers, as well as suicide bombings. Once you leave the city, it's a different story again. Move east into Zabul province or northwards to Uruzgan itself and once more you are confronted with huge swathes under effective Taliban control, where the Afghan National Army and coalition forces venture at their peril.

The security risk in much of the south is so dire that journalists cannot report on the situation there. This means the silent war being conducted in Uruzgan in part by US forces based in Kandahar Airport goes entirely unreported. One senior aid-worker briefed by the military told me on condition of anonymity that "they're having serious problems there. Why are they doing artillery drills at the [airport] base? Why is the flight traffic so busy there?" The wish to keep troop casualties to a minimum means that they must resort - as the British were forced in 1919, and as the US is now being forced in Iraq - to aerial bombing.

In the south, Afghans are afraid to travel and work. Most of my friends were worried about my plans to take the road from Herat to Kandahar, saying that even they wouldn't travel down it. Once you leave the main road, though, the risk increases exponentially. Ahmed Kandahari is the manager of a road reconstruction project in the north of Helmand province, where British troops are destined. He said that much of that area (particularly around the town of Bagran) is under the control of Taliban and Al Qaeda forces. His own security advisors tell him that each time he goes there he risks his life. Indeed, one of his engineers was recently killed travelling back home. Even the larger towns of Lashkar Gah and Qereshk are unsafe to work in. Helmand province is the hub of the country's drug trade.

The single issue that unites all the problems in the south is the drug trade. 90% of the world's heroin comes from Afghanistan, and the profits derived form a massive $2.7bn annually according to the United Nations Office on Drugs and Crime (UNODC). That makes up 52% of the country's entire GDP. A senior veteran of the Interior Ministry told Newsweek reporters that, "if we don't crack down on these guys soon, it won't be long until they're in control of everything".

One of the main problems is the involvement of government officials in the trade. In the second half of 2005 President Karzai faced a spate of resignations over the issue, and over claims of his reluctance to confront the issue. Indeed in a study for the Afghan Research and Evaluation Unit - an independent research organisation headquartered in Afghanistan - the expert Andrew Wilder concluded that at least 17 newly elected MPs are drug traffickers themselves, 24 others are linked to criminal gangs, 40 are commanders of armed groups and 19 others face serious abuse and war-crimes allegations. The elections held last year seem to have merely legitimised the status quo, and are already being referred to as "a lost opportunity" in diplomatic and NGO circles.

Government policy has had mixed success. The UNODC reported a 21% reduction in the total area cultivated in 2005, but still good weather conditions meant that this only reduced the total crop yield by 2%. Prices have also risen this year, meaning more farmers are planting the poppy. I myself stood in a large field outside Kandahar City which had been seeded for precisely this reason.

The government tends to direct its efforts at the farmers, however, and not the traffickers and officials involved higher up the chain. Karzai's reluctance - he is admittedly in an extremely tricky situation - to tackle the problem of warlords and drug lords in positions of power and influence is the single most popular source of complaint for most Afghans I talked to all over the country.

The wealth earned from that same drug trade is clearly in evidence in Kabul city. New houses are rising in the more fancy districts of the capital. One building contractor claimed recently that 70% of the new buildings being built were financed by drug money.

An alternative for farmers delivering anywhere near similar profits is yet to be found. Karzai proposed melons and pomegranates over the summer as a solution. However, poverty and a distance from the effects of their product mean that many farmers will continue cultivating poppies despite government threats of fines and imprisonment. A sensible and well reasoned report by the Senlis Council recently suggested legalising the drug in order to produce medical drugs, as already happens to some extent in Turkey. Talk of legalisation was, needless to say, rejected outright by both US and Afghan governments.

Meanwhile, drug use is rising in Afghanistan - itself notable in a Muslim country. The UNODC estimates that there are currently 170,000 users - about 1.4% of the population - of which around 30,000 are women.

Drugs, therefore, is the issue that a proposed NATO troop expansion will ultimately be forced to deal with. The US signed a long-term security partnership with Afghanistan in May, but will nevertheless press forward with plans to reduce troops from 19,000 to 16,500. They will remain in the east of the country, but only until NATO is ready to take command there too.

Andrew Elmes, the British spokesman for the UK NATO contingent said that their role will be "primarily peacekeeping", unlike the US forces who have been initiating battles with the insurgents. Other British representatives have expressed their "total commitment" to ending the drug trade in Helmand province. This confusion of presentation reflects a general discomfort among NATO allies about the coming deployment.

Ali Jalali, who had resigned from the Cabinet allegedly over the issue of drugs, commented that, "the threat in the south is terrorism, drug trafficking and organised crime; if they don't get involved in fighting these things, what will they be providing for the security of the country?" Numerous comments over the past few days suggest the British and Dutch governments will do almost anything to limit the risk to their troops, even if this means the real issues aren't confronted.

Afghans I talked to in the south seemed tentatively supportive of the NATO expansion. Most experienced on a daily basis the effects of the security situation: ranging from an inability to travel safely after sundown, to the massive inequality in education as mentioned above. Many look back nostalgically to the Taliban as providers of security. This year, everyone acknowledges, the problem is particularly acute.

Normally the winter heralds a lull in fighting, as fighters lose their mobility on account of snow and so they lie low till spring. From all sides, though, I heard that the fighters remained in their positions this winter. A cursory glance at the list of violent incidents in December confirms this.

Suicide bombers moved north and east to Mazar-e Sharif and Herat, where they have previously never been found, another consequence of allowing the conflict in the south and east to spread throughout the country. Kandahar remained subject to increasingly regular suicide bombings, thus also curtailing movement of NGOs in the south. In a message purportedly from Mullah Omar, the former Taliban leader, “stronger” tactics were promised for the new year.

Spring normally brings a new offensive, and everyone in a position to know says that this spring is likely to be even fiercer than in previous years, what with new techniques and hardware, as well as battle-hardened fighters of Pakistani and Chechen nationality crossing over from Pakistan. One source I met in Kandahar City offered me a list of madrassas (Muslim religious seminaries) in Pakistan and Afghanistan where I could find Chechen and Arab fighters waiting out the winter.

So the cost is likely to be high, regardless of whoever in the end draws the short-straw of a mission in south Afghanistan. This was the year, after all, that almost 1600 were killed including 92 US soldiers: the worst year since the overthrow of the Taliban in 2001.

Consequences of a failure to deploy on the part of the Britain are similarly dire, though. The drugs trade will envelop what's left of the country to envelop, with a consequent rise in insecurity and terrorism. There have been reports that Al Qaeda is looking for a new base for its fighters outside Iraq. Welcome to Afghanistan. NGOs are unable to work in a region where aid-workers are specifically targeted for their alleged association with the government.

In October 2001 Tony Blair boldly proclaimed to Afghans that "this time we will not walk away from you", as the Taliban were overthrown; this statement clearly in reference to the departure of US support and aid in the early 1990s following Soviet troop withdrawal from the country. I would so like to be able to imagine a positive end to this tale of hesitancy and half-heartedness. The Afghans - a brave, generous and culturally rich people -, whose traditions expect a verbal promise be honoured, deserve our support, but I fear their hopes for peace and security will remain just that. Hopes.