International forces in Afghanistan are facing mounting security problems. The Taleban - ousted from Kabul in the 2001 US-led invasion - have regrouped over the last couple of years, and are now a resurgent force in the south and east of the country.
Afghanistan presents many challenges for US, British and other forces
Although there are no reliable estimates of their current manpower, Taleban tactics are nothing new.
Their fighters follow exactly the same principles of low-level guerrilla warfare as the mujahideen fighters who inflicted heavy losses on the Soviet army which occupied Afghanistan from 1979-89.
Leading defence analyst Colonel Christopher Langton from the International Institute for Strategic Studies told the BBC News website: "It's a well-practised Afghan way of operating. There has been no change in tactics since 2001. A far as they're concerned, it works.
"They're limited by the type of equipment they have. It's been a long time since they operated any tanks or armoured vehicles.
"They don't have any aircraft, they may have some anti-aircraft missiles. But they have an abundant supply of small arms and light weapons and ammunition."
Speed, surprise, mobility and flexibility are integral factors in such 'asymmetric' campaigns; where a smaller, irregular force faces a far larger, better-armed one. The history of such encounters often shows that the smaller, local force will fare better.
Favoured guerrilla methods include ambush, sabotage, roadside bombings and assassination.
Afghanistan analyst Ayesha Khan from the UK-based Chatham House organisation said: "In the past six months the Taleban have certainly grown in confidence and momentum.
"They're increasingly employing bolder, more violent tactics such as suicide bombing and roadside bombs which we've seen in Iraq, and they're operating in larger units. "
Taleban fighters often operate as a 'pick-up truck cavalry' force of adapted four-wheel drive vehicles such as the Toyota Hi-Lux. Nicknamed Ahu (the deer) these trucks are renowned for their sturdy design and reliability, and offer good manoeuvrability across harsh terrain.
They can carry up to ten guerrillas armed with heavy machine guns and rocket-propelled grenades, who fight either from the back of the moving truck, or dismount and adopt ground positions.
Colonel Langton told the BBC: "The Toyota is not just a mainstay, they exist in large quantities across the country. They're a vehicle of convenience - they don't have to ride horses, camels or walk. And they go anywhere."
Snatch Land Rover
Defences: Armour to protect against explosions and ballistics; roadside bomb detectors
Strengths: Quick land transport for up to six troops
Weaknesses: Questions over level of protection offered
Cost: Approximately £50,000
Toyota Hi Lux
Defences: Some carry RPG launchers, heavy machine guns
Strengths: Hard-wearing, fast, reliable off-road transport for up to 10 Taleban fighters
Weaknesses: No armour, variable levels of mechanical support
Cost: Approximately $10,000 in local terms
Such a force can be quickly mustered into a surprise attack and equally quickly dispersed afterwards.
In isolation, Taleban vehicles often display no outward sign of their military purpose allowing them to blend into everyday scenery in towns and villages.
Motorbikes and push-bikes are also favoured as relatively quick, cheap and easy means of travelling distances over rough ground.
Fighting units of Taleban consist mainly of Afghans, though according to recent reports numbers of Arab and Uzbek fighters may also be involved. Groups of fighters are usually organised along local/tribal lines and led by a senior, experienced commander.
Such units are sometimes amalgamated to form bigger contingents for more large-scale operations.
Main weapons: Standard issue SA-80 rifle, L1A1 12.7 mm Heavy Machine gun, 81mm Mortar
Strengths: Highly-trained, well-supported professional soldier with modern equipment. Air support available
Weaknesses: May struggle to adapt to fighting in the harsh Afghan environment. Poor local intelligence cited as factor in recent attacks
Main weapons: Kalashnikov AK-47 assault rifle, Rocket-Propelled Grenades, Stinger missiles
Strengths: Tenacious, well-supplied guerrilla force highly adapted to local climate and geography
Weaknesses: Vulnerable to air attack. Few heavy weapons. Factional nature can mean shifting loyalties. Poor weapons-handling skills
Afghan fighters are renowned for their tenacity and ability to fight in high-temperatures and often at high-altitude.
Colonel Langton said: "If they have a weakness, it's that they're a very much traditional organisation and by looking at their fighting and cultural traditions, you can see some things that are predictable.
"They're not easy to combat though because their low-level fighting skills are highly developed."
The weapons used by the opposing forces in Afghanistan are the products of two very different eras.
The SA80, mainstay of British forces for around 20 years, has been dogged by problems involving its design and reliability but reports of battlefield problems have diminished since a multi-million pound re-fit.
By contrast the AK-47 has been in service in one form or another since the 1950s and, although the weapon of choice in many standing armies, has become a symbol of guerrilla struggle thanks to its reputation for ruggedness and simplicity of use.
Developed: 1970s/ 1980s
Magazine capacity: 30
Loaded weight: 5kg (11lbs)
Range: 500m (1,641ft)
First made: 1947
Magazine capacity: 30
Loaded weight: 3.6kg (7.9lbs)
Range: 300m (984ft)