After the fall of the Afghanistan government, men fled over the porous border with Pakistan and found refuge in the inhospitable and mountainous territory of Waziristan.
 
There they paid local tribal leaders for their support against Pakistan's security forces.
 
Al-Qaeda elements are believed to hide in the same terrain, planning their assaults against US and other Western nations.
 
The Taliban and al-Qaeda have close ties. The US invaded Afghanistan on the pretext that the government would not hand over Osama bin Laden, the leader of al-Qaeda in Afghanistan.
 
In Pakistan, the Taliban has been able to set up bases of organisation and has regrouped. They have increasingly launched attacks in Swat and Bajaur in 2008.
 
Afghan attacks
 
Professor Paul Wilkinson, chairman of the advisory board at the Centre for the Study of Terrorism and Political Violence at St Andrews University, Scotland, said that the Pakistani Taliban is the Taliban on Pakistan soil, helping to relaunch its efforts to regain control of Afghanistan by sending weapons, other materials and launching attacks into nearby regions of Afghanistan.
 
"They are not attempting to take control of Pakistan regions, that would be impracticable," he told Al Jazeera.
 
 
"I don't think Pakistan sees this as a frontal challenge to their own ability to maintain an independent government.
 
"It is not a question of a Taliban threat to Pakistan directly.
 
"It is more a question of Taliban using handy resources of space, suitable terrain in which to hide, in order to continue their campaign.
 
"They are using their situation in pretty favourable terrain and among a pretty favourably inclined population to plan and pump logistic support across the frontier to help the people who are actually fighting in Afghanistan. It's an enormous help to them.
 
"The Pakistan army is unable to stop weapons and other materials from getting across the border to Afghanistan. That is a big problem for Nato in Afghanistan who is trying to fight the Taliban there."
 
The Taliban in Pakistan works in small groups and are highly mobile, carrying out surprise attacks on military and civilian targets often causing a large number of deaths. Although it is difficult to say how many members it has, its nucleus may number several thousand.
 
Those Pakistanis whose support they have been able to buy are typically jobless Pashtun tribesmen.
 
They do not have a single leader, but look to the Afghan Mullah Mohammad Omar as a symbol and iconic figure for their movement.
 
Taliban members are motivated by the belief that they will succeed in regaining control of Afghanistan.