By M Ilyas Khan
BBC News, Karachi
Pakistan's tribal district of South Waziristan, on the border with Afghanistan, is in the throes of turmoil once again.
The militants have imposed their authority in much of the tribal areas
The government says that the local tribesmen have started an armed campaign to expel foreign militants whom it blames for launching cross-border attacks on foreign and Afghan troops in Afghanistan.
It says more than 250 people, mostly foreign militants, have been killed in these clashes since early March.
Unofficial reports put the casualty figures much lower, and suggest that mixed groups of local and foreign militants are confronting each other in what also appears to be a power struggle within the tribes.
Both claims are difficult to verify. Journalists have been denied access. Mobile phones do not work in the area. Landline phone connections remain dead after a robbery in the telephone exchange two months ago.
But interviews with truckers and residents who have been moving in and out of the region clearly show that while the above two views may be partially correct, there is also a third dimension to this conflict.
The Ahmadzai Wazir tribe dominates the western parts of South Waziristan agency, and as such controls the economically lucrative border trade routes between Afghanistan and Pakistan.
The largest of its nine sub-tribes is the Zalikhel, which controls Wana, the administrative and financial capital of the district, and has traditionally provided leadership to the smaller sub-tribes.
Within the Zalikhel, there are three clans of which the largest is the Yargulkhel, the actual harbourers of foreign militants in Wana.
The Yargulkhel clan produced a number of Taleban commanders, notably Nek Mohammad, who brought thousands of foreign militants to Wana in 2002-03 and inflicted a crushing defeat on the Pakistan army in fighting in March 2004.
He was killed in a US air strike in June 2004, prompting the fractious Yargulkhel commanders, including his brother Haji Omar, to start asserting their authority and open separate Taleban offices in Wana.
The present conflict has seen some of these Yargulkhel commanders arrayed against Mullah Nazir, who was appointed by the top Taleban leadership as the chief commander of Ahmadzai Wazirs in November 2006.
The Yargulkhels may be upset because Mullah Nazir hails from an obscure sub-clan of the Zalikhel's least numerous clan, the Kakakhel.
That appears to be one source of the violence.
If this is the case, then where do the foreign militants stand in this free-for-all?
The government says that they are being hunted by the local tribesmen, but reports from Wana suggest that only Uzbeks are the target of Mullah Nazir's fighters.
The death of Nek Mohammad provoked outrage among his supporters
The real al-Qaeda - the Arabs - find no mention in either official or unofficial reports from Wana.
Other groups that remain quietly in the background are the Chechens, some ethnic Uighur Chinese and a large number Kashmiri and Pakistani sectarian groups known in Afghanistan and the Pakistani tribal areas as the 'Punjabi' mujahideen.
Until recently, it was believed that the Uzbeks were divided into two mutually hostile groups, one Wana-based and headed by Qari Tahir Yuldashev, and the other led by Nasir Sohail who is based in the town of Mir Ali in the neighbouring North Waziristan tribal district.
Officials now say that there is a third Uzbek group in Wana - the so-called 'good guys' who are helping the local tribesmen get rid of Mr Yuldashev's bad guys.
Mullah Nazir has accused Mr Yuldashev's men of killing more than 200 tribal elders in the region during the last two years after labelling them as US spies or Pakistani agents.
Most local people believe the Uzbeks alone are not to blame, but in some recent cases it became apparent that they had served as hired guns for tribesmen who wanted their enemies eliminated.
Matters came to a head on March 6, 2007, when some Uzbek gunmen tried to kill a tribal elder in Azam Warsak, 12km west of Wana, sparking a clash in which 19 persons, including 12 Uzbek fighters, were reported killed.
Clashes broke out again on March 20 following the murder of an Arab militant commander which Mullah Nazir blamed on the Uzbeks.
Since then, intermittent clashes between the two sides have continued, leaving close to 100 people, including more than 10 military personnel, dead.
One major question is, how could a tribally weak person like Mullah Nazir succeed where powerful Yargulkhel commanders have failed?
A tribal council has called for the eviction of the Uzbeks
The answer brings us to the third dimension of our story.
Beginning late last September, a large number of previously unknown mujahideen (holy fighters) - some sources put their number at more than 2,000 - started to descend on the villages of Wana and took up accommodation, paying generous amounts of rent.
The local people initially thought they had come from Turkmenistan, but many now suspect they are linked to the Pakistani military.
The newcomers picked fights with the Uzbeks and created tensions that led to an all out confrontation in November 2006 between different groups vying for the control of Wana.
The situation was defused by some top Taleban leaders who crossed over from Afghanistan and appointed Mullah Nazir as the chief commander of the Ahmadzai Wazir tribe.
The newcomers as well as the Punjabi mujahideen have since thrown their weight behind Mullah Nazir, enabling him to hold his own against powerful Zalikhel and Yargulkhel commanders.
Recently, even the top Taleban emissaries failed to force him to agree to a truce with the Uzbeks and their tribal supporters.
On Wednesday, his volunteers were able to dislodge their opponents from their well-entrenched positions in Shin Warsak, a village west of Wana, and there is talk that the Uzbeks might decide to surrender over the next couple of days.
It appears that the Pakistani government has been able to exploit group differences among the militants and has isolated the Uzbeks.
The way ahead lies in two directions.
First, the government could try to consolidate its gains and isolate the Arabs and other militants in the region in the next phase. This would also mean initiating similar action against foreign militants and their local supporters in North Waziristan as well.
The government would probably only follow this course if it has made up its mind to abandon the Taleban for good and deal a decisive blow to militancy in the region.
The other option is to brandish the high casualties among 'foreign militants' to ward off international pressure for some time, without hurting the interests of the Taleban militants beyond repair.
So far, the second course has been Islamabad's preferred way of dealing with the western powers whose troops are battling the Taleban in Afghanistan.
Will it be different this time?