In the cloistered circles of the Taliban high command, Mullah Abdul Ghani Baradar had no equal.
As military chief of the hardline Islamic movement that once ruled Afghanistan and was ousted by a US-led alliance, he oversaw the campaign of ambushes and roadside bombings that proved his fighters could threaten the most advanced armies.
When the talismanic leader was caught in Karachi in 2010, some Afghan officials hoped the magnetism he forged in war would persuade his former comrades to start talking peace. Indeed, news that Islamabad had allowed Afghan officials to visit Baradar two months ago sparked speculation in both countries of the prospects for a settlement.
Instead, Pakistan's refusal to hand him over to Afghanistan symbolises one of the biggest obstacles to negotiations: a legacy of bone-deep suspicion dividing the neighbors.
Afghanistan fears that Pakistan is only pretending to support dialogue while its intelligence agencies harbour Taliban leaders to project influence across their shared frontier.
Any move to repatriate Baradar would raise Afghan hopes that Pakistan is willing to play a genuinely constructive role and open the door to other prominent insurgents.
"Releasing Mullah Baradar would encourage other Taliban leaders to embrace reconciliation," Ismail Qasemyar, an adviser to Afghanistan's High Peace Council, told Reuters. "It would be a huge symbolic step."
Members of the council, who are charged with reaching out to insurgents, aim to visit Islamabad in the next few weeks to make a fresh plea for Pakistan to allow Baradar to return to Kabul as a guest of the Afghan government.
With the United States and its allies due to withdraw the bulk of their combat forces by the end of 2014, pressure is mounting on President Hamid Karzai to start meaningful negotiations with the Taliban and prevent violence spiraling.
But there is no guarantee Pakistan will agree to release Baradar, or that he retains enough influence to play a decisive role.
"We are fully cooperating with Afghanistan in whatever they are asking for the peace process," Interior Minister Rehman Malik said in a recent interview.
"For developing peace in Afghanistan, we are giving every kind of help. We have given access."
He did not comment further on the subject.
The Afghan government believes Baradar is more amenable to dialogue than many of his comrades.
In the months before his arrest, Baradar authorised contacts with United Nations representatives to explore the possibility of dialogue, according to former UN and Taliban officials.
Afghan officials believe Pakistan detained him as part of a broader strategy to retain a veto over any eventual settlement in Afghanistan.
More cautious voices argue that negotiations will only work if Karzai broadens his strategy of lobbying prominent insurgents to defect into a wider process to address the roots of Afghanistan's conflict.
Taliban folklore has it that Baradar was present on the day in 1994 when Mullah Mohammad Omar, the Taliban's leader, launched his campaign to cleanse Afghanistan of rapacious warlords by hanging one particularly loathsome militia chief from the barrel of a tank.
Their friendship bolstered Baradar's stature during the Taliban's march on Kabul and its 1996-2001 reign. The Taliban government collapsed after the United States and its allies attacked Afghanistan for harboring al Qaeda leader Osama bin Laden, the architect of the Sept 11, 2001 attacks in New York and Washington.
Baradar would later emerge as Mullah Omar's second-in-command, translating spiritual guidance into orders as the Taliban insurgency gathered strength.
Mullah Omar bestowed him with the nom de guerre "Baradar," which means "brother". Although a ruthless fighter, Baradar had a knack for forging compromise, another trait that appeals to mediators.
Baradar was captured in early 2010 in Karachi in a joint operation between Pakistani intelligence officers and the CIA.
Some argue that more than two years in detention have eroded his sway over an evolving insurgency.
The Haqqani network, which is alleged to have used havens in Pakistan to launch attacks on Kabul, is showing signs of growing independence from the Taliban hierarchy.
And a blistering campaign of US night raids on Taliban commanders has weakened Mullah Omar's chain of command.
What does seem certain is that Baradar's return would give Karzai's outreach more credibility among Pashtuns, the community that dominates southern and eastern Afghanistan, where the insurgency is strongest.
The captive's mystique is burnished by his status as the highest-ranking Taliban commander to hail from the Popalzai, the same Pashtun sub-group as Karzai.
"If Mullah Baradar joins the government, 80 per cent of the problem with the Taliban will be solved," said Haji Obaidullah Barakzai, a lawmaker from Uruzgan, the southern province where Baradar was born.
Leap of faith
Pakistan allowed Afghan officials to meet Baradar in detention. However, repatriating Baradar would require a much bigger leap of faith.