As information poured in on Friday that Pakistani Taliban leader Baitullah Mehsud was killed two days ago by a U.S. missile strike, a whole series of questions arise over what it would mean for Pakistan, Afghanistan and US policy and Western military forces in the region.
The following is look at the possible repercussions for the war against Taliban guerrillas in the borderlands between Afghanistan and Pakistan.
Will it help western forces in Afghanistan?
Probably not much, at least directly, according to some senior diplomats in Islamabad.
But the United States will be happy to have eliminated a militant leader whose actions were destabilising Pakistan to the point where concerns were growing over the safety of the Muslim nations nuclear assets.
Mehsud may have controlled the largest number of fighters, variously reckoned at between 10,000 and over 20,000, and they have mounted attacks on Western forces in Afghanistan, but they have mostly attacked the Pakistan government and security forces over the past two years.
The Mehsud stronghold in the mountains of South Waziristan is not contiguous with the Afghan border.
One diplomat watching military affairs said that strategically, Mehsud was effectively helping to guard the back of those Taliban factions located next to the border and who are heavily involved in the Afghan insurgency.
These groups include Maulvi Nazir Wazir in South Waziristan and Hafiz Gul Bahadur in North Waziristan, who both control more than 5,000 fighters apiece. And also the powerful Haqqani faction that operates mainly out of North Waziristan and southeast Afghanistan. The United States and other Western allies hope that Pakistan will one day turn on these groups, as well as the Afghan Taliban using Pakistan's southwest Baluchistan as their safe refuge. Analysts say Pakistan has failed to take on any of these groups seriously, and in some cases adopts a permissive stance.
Would Mehsud's death help pacify Pakistan?
His death is a major coup for Pakistan.
It shows efforts to push back the Taliban tide in the northwest going in the right direction, with the army already in the final stages of a campaign to clear the insurgents out of Swat, a valley far to the east, closer to the capital Islamabad.
But the removal of Pakistan's Public Enemy No. 1 leaves open the question of whether the army will now carry out any major ground offensive against Mehsud's stronghold.
The terrain is perfect for guerrilla warfare and the army would be up against far more battle-hardened fighters, including Uzbeks and Chechens, than they encountered in Swat, so the risk of heavy casualties was high.
Some analysts believe the more likely strategy will be to keep routes in and out of the Mehsud lands blocked, while continuing air attacks, and also seeking to isolate the Mehsuds from other Taliban factions with different tribal loyalties.
Meantime, there is a clear risk of revenge attacks by Mehsud's loyalists inside Pakistan.
Qari Hussain, one of Mehsud's lieutenants, is regarded as the main overseer of the suicide bomb campaign and other high profile attacks inside Pakistan, and he is still alive.
Hussain belongs to the Mehsud tribe but he is also a member of Lashkar-e-Jhangvi, a militant group based in the central province of Punjab that forged ties with al Qaeda well before the September 11 2001 attacks on the United States.
What does it say about the state of US-Pakistan relations?
It shows the US and Pakistan military are working closely together, regardless of Pakistan's public opposition to US drone attacks on Pakistani territory.
CIA-operated drone aircraft began targeting Mehsud territory in June, after the Pakistani government told its army to go after the militant leader.
There is a chance that the United States might have an understanding with Pakistan on which Taliban groups to focus on next, which could also hurt the Afghan insurgency.
Who could take over from Mehsud?
Mehsud was the Taliban commander with the clout to forge a single group out of the various Taliban factions in Pakistan, and his successor might struggle to impose himself within the loose-knit confederation of regional commanders.
The leader of the Afghan Taliban Mullah Mohammad Omar will undoubtedly play a role in trying to unify competing chieftains.
The hot favourites to become the new head of the Pakistani Taliban are: Hakimullah Mehsud, Maulana Azmatullah and Wali-ur-Rehman.
Hakimullah Mehsud commands an estimated 8,000 fighters in three tribal regions -- Orakzai, Khyber and Kurram -- and is an important leader in the Taliban hierarchy.
Azmatullah also hails from the Shahbikhel, the same branch of the Mehsud tribe that Baitullah Mehsud's Bromikhel clan belongs to. He is an important commander and a member of the Pakistani Taliban shura, or council of leaders.
Wali-ur-Rehman is another shura member, and is a former spokesman for Baitullah. Some analysts see him as the most likely contender to take over Mehsud's group if not the whole Taliban movement in Pakistan.