The rescue of an abducted US-Canadian family in Pakistan last week has spotlighted their captors the Haqqani Network, former CIA assets now considered one of the most dangerous factions fighting US-led Nato forces in Afghanistan.
Led by Sirajuddin Haqqani, who doubles as the Afghan Taliban's deputy leader, the militant group has been blamed for spectacular attacks across Afghanistan since after the US invasion.
"When you hear US officials, including in private settings, talking about what worries them the most, they always talk about the Haqqanis," said analyst Michael Kugelman, of the Wilson Center in Washington.
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Who are they?
The group was founded by Jalaluddin Haqqani, an Afghan mujahideen commander fighting the Soviet occupation of Afghanistan in the 1980s with the help of the US and Pakistan.
Jalaluddin gained notoriety for his organisation and bravery, garnering attention from the CIA and a personal visit from US congressman Charlie Wilson.
A fluent Arabic speaker, Jalaluddin also fostered close ties with Arab militants, including Osama Bin Laden, who flocked to the region during the war and later became a minister in the Taliban regime.
Now designated a militant group by the US, the Haqqanis are known for their heavy use of suicide bombers. They were blamed for the truck bomb deep in the heart of Kabul in May that killed around 150 people - though Sirajuddin later denied the accusation in a rare audio message.
The network has also been accused of assassinating top Afghan officials and holding kidnapped Westerners for ransom.
That includes recently released Canadian Joshua Boyle, his American wife Caitlan Coleman, and their three children - all born in captivity - as well as US soldier Bowe Bergdahl, who was released in 2014.
Where are they now?
Following the US invasion of Afghanistan, Taliban fighters flooded across the border into Pakistan, where they regrouped.
That included the Haqqanis, who coordinated attacks on Nato from across the border in their stronghold of Miran Shah.
The US has launched repeated drone attacks targeting the group - including one late Monday - while Pakistan's military has conducted successive clearing operations.
Pakistan intensified a military operation in the area in 2014, however, and some militant sources say the pressure has forced many of the Haqqanis underground or over the border into their Afghan strongholds, claims that AFP could not confirm.
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What does the US want Pakistan to do?
Washington has long pressured Pakistan to crack down on militant groups, with the Haqqanis a top priority.
US President Donald Trump turned up the heat this summer when he accused Pakistan of playing a double game in Afghanistan and upbraided Islamabad for sheltering "agents of chaos".
Islamabad has repeatedly denied the claims and accused Washington of ignoring the thousands of Pakistani lives lost in its struggle with militancy.
The recovery of Boyle, Coleman, and their children came weeks later, with Pakistan using its role in securing their freedom to urge the US to trust it is doing its best.
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