The appointment of hardline cleric Mullah Fazlullah as chief of the Pakistan Taleban is likely to mean a period of more bloodshed as he tightens his grip on a faction-ridden group.
To stamp his authority, he will have to avenge the death of his predecessor, Hakimullah Mehsud, who was killed in a US drone strike on Nov 1, analysts say.
"Fazlullah will have to show he is capable and terrorist acts by the group will become necessary," said Dr Ajai Sahni, head of the New Delhi-based Institute of Conflict Management.
"Killings decide the survival of terrorist groups," he told The Straits Times.
That is especially since Fazlullah is the first outsider in a group dominated by the Mehsud clan of Waziristan province.
A compromise candidate after the Mehsuds could not agree on a leader, his immediate priority will be to prevent other leaders from splitting the group.
One of the most feared militant groups in Asia, Fazlullah's Tehreek-e-Taliban Pakistan (TTP) has been blamed for most of the recent attacks in Pakistan, including the assassination of former premier Benazir Bhutto. After Osama bin Laden's death in 2011, the group claimed responsibility for bombing the paramilitary force academy in north-west Pakistan and an assault on a naval base in Karachi.
Thirty-nine-year-old Fazlullah came to be known as the "butcher of Swat" during his rule of the valley between 2007 and 2009, turning the tourist spot into one of the bloodiest as he set up a parallel government and pushed for hardline syariah laws.
Images of him riding his black stallion and flashing a double-edged sword as he led his forces into the interiors of Swat valley remain etched in the minds of those who have witnessed the transformation.
During his peak, he was said to be backed by more than 5,000 hardliners and had a commando squad of over 1,000 members before he was driven out of Pakistan by the military in 2009. Mentored by his father-in-law, Sufi Mohamed, an influential religious leader who initiated a campaign for syariah laws through his organisation, the Tehreek-i-Nafaz-i-Shariat-i-Muhammadi (TNSM), Fazlullah fought against US forces in Afghanistan after the 9/11 attacks.
Both he and his father-in-law were arrested. Sufi was sentenced to 10 years in prison. Fazlullah was released in 17 months. He returned to Swat to fill the void created by his father-in-law's absence. TNSM was aligned with TTP and he became the new ameer (leader) of Swat.
Fazlullah's fiery speeches and radio sermons began to impress many, particularly women, who encouraged their men to be more conservative.
The hardline cleric encouraged mothers not to send their girls to school, destroyed more than 400 schools and burnt piles of TVs and computers, which he deemed "un-Islamic".
He urged parents to refrain from inoculating their children against polio, which he called a ploy of the West to cause infertility and impotency - a tragedy, given that polio incidents are surfacing all over again in the northern parts of Pakistan.
As his following grew, so did his fanaticism. More than 300 supporters of the nationalist Awami National Party that had support in the valley were killed. Many wrongdoers were flogged and beheaded, with bodies hung from electric poles. Green Square in Mingora, in Swat, came to be known as "Bloody Square".
"Fazlullah will transform the TTP from a tribal to an ideological Islamist group," said Swat-based terrorism analyst Zia-ur-Rehman.
"It will become more violent and its motive will be to impose syariah rule."
The likelihood of the cleric's return from Afghanistan - he is said to be hiding in the Afghan province of Nuristan - to Pakistan is being watched as TTP has global aspirations and he is backed by Mullah Omar, who heads Afghan Taleban.
TTP claimed responsibility for the suicide attack on the US airbase in Khost and for the 2010 car bombing attempt in New York's Times Square.
"Fazlullah is a capable firebrand extremist," says Dr Sajjan Gohel, a London-based terrorism expert. "He is the one who talebanised Swat. And right now he will be under pressure to act."
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