Kabul's writ has never run strong in the remote southern plains of Helmand province. For this reason, it has emerged as the most significant Taliban stronghold in Afghanistan.
Since 9/11 this region has been in turmoil. In the Baramcha area on the Afghan side of the border, the Taliban have a major base. From there they control militant activities as far afield as Nimroz and Farah provinces in the west, Oruzgan in the north and parts of Kandahar province in the east. They also link up with groups based in the Waziristan region of Pakistan.
Commander Mansoor Dadullah, a one-time Taliban chief of the province who has since developed differences with the Taliban leadership, comes from Helmand, but he has currently shifted his operations to Zabul province and across the border into Balochistan.
Taliban from Baramcha region move freely across the border, and often take their injured to hospitals in the Pakistani town of Dalbandin in Chaghai.
The Helmand Taliban have been able to capture territory and hold it, mostly in the south of the province. They constantly threaten traffic on the highway that connects Kandahar with Herat.
Kandahar has the symbolic importance of being the spiritual centre of the Taliban movement and also the place of its origin. The supreme Taliban leader, Mullah Mohammad Omar, made the city his headquarters when the Taliban came to power in 1996. Top al-Qaeda leaders, including Osama Bin Laden, preferred it to the country's political capital, Kabul.
But the Taliban have a strong presence in the countryside, especially in southern and eastern areas along the border with Pakistan. Afghan and Western officials have in the past said the Taliban have used Quetta, the capital of the Pakistani province of Balochistan, as a major hideout as well as other Pakistani towns along the Kandahar border.
Areas on the Pakistan side stretching north-eastwards along the border from Quetta to the town of Zhob are inhabited by Pashtun tribes.
Taliban activity in Balochistan is largely related to operations inside Afghanistan and is of no immediate concern to Islamabad.
Afghanistan's Zabul province lies to the north of Kandahar, along the Toba Kakar mountain range that separates it from the Pakistani districts of Killa Saifullah and Killa Abdullah. Taliban insurgents use the Toba Kakar passes when infiltration through South Waziristan is difficult due to intensified vigilance by Pakistani and Afghan border guards.
Zabul provides access to the Afghan provinces of Ghazni, Oruzgan and Kandahar. There are few Afghan or foreign forces in the area, except on the highway that connects Qalat, the capital of Zabul, to Kandahar in the south-west, and Ghazni and Kabul in the north.
As the Pakistani military strategists who organized Afghan guerillas against the Soviets in the 1980s discovered to their delight, Kurram is the best location along the entire Pakistan-Afghanistan border to put pressure on the Afghan capital, Kabul, which is just 90km (56 miles) away.
The Taliban, with their primary interest in the war in Afghanistan, have also steered clear of Orakzai tribal district because it does not share a border with Afghanistan and is therefore of no strategic value.
Taliban sanctuaries in South Waziristan and North Waziristan directly threaten Paktika, Khost and Paktia provinces of Afghanistan. The US-led forces have large bases in the Barmal region of Paktika and in Khost, and several outposts along the border to counter infiltration. Pakistani security forces also man hundreds of border checkposts in the region.
However, infiltration has continued unabated with many hit-and-run attacks on foreign troops.
Tribal identities are particularly strong in Paktika, Khost and Paktia. During the Taliban rule of 1997-2001, these provinces were ruled by their own tribal governors instead of the Kandahari Taliban who held power over the rest of the country. In the current phase of the fighting they co-ordinate with the militants in Kandahar and Helmand, but they have stuck with their own leadership that dates back to the war against the Soviets in the 1980s.
South Waziristan, a tribal district in Pakistan's Federally Administered Tribal Areas (Fata), is the first significant sanctuary Islamic militants carved for themselves outside Afghanistan after 9/11. Militants driven by US troops from the Tora Bora region of Nangarhar province in late 2001, and later from the Shahikot mountains of Paktia in early 2002, poured into the main town, Wana, in their hundreds. They included Arabs, Central Asians, Chechens, Uighur Chinese, Afghans and Pakistanis. Some moved on to urban centres in Punjab and Sindh provinces. Others slipped back into Afghanistan or headed west to Zhob and Quetta and onwards to Iran. But most stayed back and are fighting the Pakistani army.
Unofficial estimates by informed circles put the current number of these foreign fighters at "several hundred". They have concentrations in parts of South and North Waziristan and Bajaur in Fata region, and have also fanned out to conflict zones in Pakistan's North West Frontier Province (NWFP), such as Swat and Buner.
The eastern half of South Waziristan is inhabited by the Mehsud tribe and the main militant commander here is Hakimullah Mehsud, who rose to this position in August, when a suspected US missile strike led to the killing of the top Mehsud commander, Baitullah Mehsud. He heads perhaps the largest militant group in Pakistan, with an estimated strength of more than 15,000 armed men, although the "hard core" of his fighters is much smaller.
The western half, along the border with Afghanistan, is Ahmedzai Wazir territory where Maulvi Nazir commands roughly 8,000 to 10,000 militants. Again, most of these cannot be considered battle-hardened and whether they would fight to the last is unclear.
The Mehsuds only live on the Pakistani side, while the Wazirs inhabit both sides of the border. This partly explains the direction the two commanders have taken over the last few years. Maulvi Nazir's men have largely focused on the war in Afghanistan, and have only recently had some problems with Pakistani forces, apparently due to continued missile strikes by suspected US drones which they believe have tacit Pakistani support.
Tehrik Taliban Pakistan (TTP), an umbrella organisation for anti-Pakistan groups operating in Orakzai, Bajaur and Swat regions, was set up in 2006 by Baitullah Mehsud, the Taliban leader killed in 2009 by a US missile.
In early 2009 Baitullah Mehsud and Maulvi Nazir entered into a three-way partnership with another ethnic Wazir commander, Hafiz Gul Bahadur, who heads the militants in neighbouring North Waziristan. Their aim was to organise joint defence if they come under attack.
But the agreement has failed to work in the wake of a military operation that Pakistani forces launched in South Waziristan in October, months after Baitullah's death. The operation has targeted the Mehsud areas and has brought several towns under army control. But it has not been extended to the Wazir areas of South and North Waziristan, neither have the Wazir groups made an attempt to come to Hakimullah Mehsud's help.
North Waziristan is dominated by the Wazir tribe that also inhabits the adjoining Afghan provinces of Paktika and Khost. North and South Waziristan form the most lethal zone from where militants have been successfully destabilising not only those provinces but others such as Paktia, Ghazni, Wardak and Logar. Groups based in the Waziristan region are known to have carried out attacks in the Afghan capital, Kabul, as well.
Current estimates put the number of armed militants in North Waziristan at more than 10,000. A much smaller number are battle hardened. They are led by Hafiz Gul Bahadur, a veteran of the 1992-96 Afghan civil war who later joined the Taliban. Like Maulvi Nazir in South Waziristan, he has largely focused on the fighting in Afghanistan and has had little friction with Pakistani forces since a 2006 peace deal. In fact, Taliban loyal to him have confronted foreign fighters based in the eastern North Waziristan town of Mir Ali, who have been attacking Pakistani troops in the region. But he, too, is perturbed over drone attacks in the region, and considers Pakistan responsible for them.
North Waziristan is also the home base of another veteran Afghan militant, Jalaluddin Haqqani. His main responsibility has been to organise Taliban resistance to Western forces in Afghanistan, but he has wielded considerable influence over the top commanders in South and North Waziristan. He is also reported to have maintained links with sections of the Pakistani security establishment and is known to have mediated peace deals between the Pakistani government and the Wazir and Mehsud commanders in the region. Mr Haqqani is now an old man, and his son Sirajuddin has taken over most of his work.
The Afghan government has a comparatively firmer grip on the situation in Nangarhar. This is partly due to the compulsion to keep the supply route for Western forces - which connects the Pakistani city of Peshawar with Kabul and passes through Nangarhar - safe.
But there are pockets of resistance in the area. The main Taliban commander here is Anwarul Haq Mujahid, son of a former mujahideen commander, Mohammad Younus Khalis. This group was responsible for offering protection to Osama Bin Laden in the Tora Bora caves soon after 9/11. In recent months militants from the region have been linking up with the so-called Haqqani network in the Paktika-Khost-Paktia region.
Analysts have long suspected Pakistan's Bajaur tribal region to be the hiding place of Osama Bin Laden, Ayman al-Zawahiri and other top al-Qaeda leaders. As such, it is where suspected US drones launched their earliest missile strikes. One drone strike in January 2006 was said to have narrowly missed Ayman al-Zawahiri, although it killed nearly 18 others. Another strike nine months later killed 80 people at a religious seminary which US and Pakistani officials said was training militants.
The dominant militant group in Bajaur, and those in the neighbouring Mohmand tribal region, became members of the Baitullah Mehsud-led Tehrik Taliban Pakistan (TTP), which was formed soon afterwards. Militants in both areas have since fought Pakistani forces inside their respective tribal zones, and have also carried out attacks in the cities of Peshawar, Charsadda and Mardan. They also conducted the first attacks against security forces in the Malakand region, where the Pakistani forces had to fight a fully fledged insurgency in and around the Swat valley earlier in the summer of 2009.
Maulvi Faqir Mohammad is the chief commander of the Taliban in Bajaur. He was said to lead a force of nearly 10,000 armed militants but there are indications the ranks have thinned in the wake of the operation in the TTP's home base of South Waziristan.
A year-long military operation against the militants in Bajaur ended early in 2009, followed by a peace agreement under which the dominant tribe in Bajaur, the Mamunds, agreed to surrender the entire TTP leadership to the government. But that has not happened. The Taliban are back in control in most areas outside the regional capital, Khaar, and Maulvi Faqir Mohammad continues to use his sermons, broadcast from an FM radio station, to whip up support for the Taliban.
Bajaur shares a border with the Afghan province of Kunar. Pakistani forces battling the Taliban in Bajaur have complained that US and Afghan troops on the other side of the border have not been doing enough to crack down on the Taliban there.
In Mohmand, about 5,000 militants led by Omar Khalid have been resisting attempts by the security forces to clear them from southern and south-eastern parts of the district in order to reduce pressure on Peshawar and Charsadda. In recent weeks, their activities have become infrequent and their grip on most of their erstwhile strongholds has loosened.
Initially the Taliban were unable to maintain sustained pressure on the country's south-central highlands. But with safe sanctuaries in the border region - from the Baramcha area of Helmand province in the south, to some parts of Pakistani Balochistan, Waziristan and Bajaur and Mohmand to the east - the Taliban now have the capacity to render roads in this region unsafe.
Training camps run by al-Qaeda and Taliban groups have multiplied in secure border regions over the past few years. Safe havens have also afforded the militants endless opportunities to find new recruits. The Waziristan region is also known to be a haven for young suicide bombers trained in remote camps. The Taliban also appear to have had access to sophisticated military equipment and professionally drawn-up battle plans.
The strategy appears to be the same as in the 1980s - "death by a thousand cuts". Sporadic attacks on the security forces and the police have grown more frequent over the years, and have also crept closer to Kabul. At the same time, the Taliban have destroyed most of the education infrastructure in the countryside, a vital link between the central government and the isolated agrarian citizenry.
Oruzgan has mostly come under pressure from groups in Kandahar and Helmand. These groups, as well as those based in the Waziristan-Paktika-Khost region, have also moved up the highway via Ghazni to infiltrate Wardak to the west and Logar to the east. Safe and quiet until less than three years ago, both these provinces are now said to be increasingly infiltrated by Taliban fighters.
But they still do not have the capacity to confront troops in open battle, or capture and keep towns.
Swat, a former princely state in northern Pakistan, was governed by a British-era law which a court declared unconstitutional in the early 1990s. That triggered a violent campaign for Islamic law to be introduced in Swat and other areas of the Malakand region of which it is part. The Swat insurgency was effectively put down in 1994 but it re-emerged after 9/11, attracting many battle-hardened militants from Waziristan, Bajaur and the neighbouring district of Dir.
The campaign of the Swat militants has been the most destructive anywhere in Pakistan. They have targeted security forces, police, secular politicians and government-run schools.
By early April 2009, Sharia law had been imposed as part of a deal between the authorities and the local Taliban. However, the militants failed to disarm completely in line with the accord and their fighters spread to neighbouring districts, prompting international concern.
In late April, Pakistani forces launched an operation in four districts of Malakand region, causing some three million people to flee the fighting. Most of the area has since been brought under control and peace has returned to large parts. Most of the refugees have also returned to their homes, though some scattered resistance by the militants remains.