On the chilly morning of December 16, seven armed men dressed in military camouflage entered an army-run school in Peshawar, the largest city in Pakistan's northwest Khyber Pakhtunkwa province. The men went from class to class, telling kids to say their prayers before shooting them at point-blank range. The massacre left 150 people dead, including 134 children.
Later that afternoon, Mohammad Omar Khorasani, a spokesman for the Pakistani Taliban, took credit for the attack.
"We want the Pakistan army to feel pain," said Khorasani, who represents the group formally known as Tehrik-e-Taliban (TTP).
A man in his late thirties with dark, glowing eyes, Khorasani counted the attack as a success in his group's fight against the Pakistani government. He said it was revenge for an army offensive that began in June in the North Waziristan tribal area, a former Taliban stronghold.
For the rest of humanity, the attack was an abomination — so brutal it was even condemned by the Taliban in Afghanistan, a separate group that has committed its own share of atrocities.
"They came with the intention of taking no hostages," General Asim Bajwa, a spokesman for the Pakistani military, told reporters after the attack. Bajwa said the Taliban's only motive was "to kill the children."
Syed Irfan Ashraf, a Pakistani counterterrorism expert, told VICE News the Pakistani Taliban is a "volatile group" that "exists in a constant state of desperation." The group's origins can be traced back to the US invasion of Afghanistan in 2002. When the war began, many Arab al Qaeda fighters fled across the border, seeking refuge in Pakistan's autonomous tribal areas. Five years later, in 2007, the Pakistani Taliban movement was born.
"The TTP has always been a joint venture comprising different factions," Hasan Abdullah, an expert on the Pakistani Taliban, told VICE News. According to Abdullah, at least 40 groups — many of which have divergent interests — joined the movement at its inception. The Arabs introduced them to al Qaeda's vision of "global expansionist Islam."
'The strategy to deal with both the Afghan and the Pakistani Taliban as the exclusive domain of the Pakistan armed forces has backfired.'
"That was the turning point, when the Arabs were given shelter by these tribes," Ahmed Rashid, the author of Taliban, Islam, Oil and the New Great Game in Central Asia, told VICE News. "With their arrival began a much deeper process of radicalization for Pakistan's fiercely independent tribes and its members."
Rashid said that, compared to their counterparts in Afghanistan, the Pakistani Taliban are "ideologically primed, more radical, vicious, and visionary."
Ayesha Siddiqa, author of Military Inc.: Inside Pakistan's Military Economy, said the difference between the Afghan and Pakistani Taliban has been exaggerated, partly as a way for Pakistan's military to justify its support of "friendly" Taliban groups that carry influence in Afghanistan, while cracking down on domestic militants that threaten national security.
Siddiqa said the Afghan Taliban still have powerful backers within the Pakistani state, but "the Pakistani Taliban movement has challenged Pakistan's military and has emerged as enemy number one."
The Mehsuds, a large and powerful tribe spread across North and South Waziristan, were key to the creation of the Pakistani Taliban. Baitullah Mehsud, the movement's founding leader, was killed by a US drone strike in August 2009. Four years later, in November 2013, Baitullah's successor Hakimullah Mehsud was also killed by a drone attack.
Two broad groups emerged from the ensuing leadership vacuum: Those who remained loyal to the Mehsuds, and those who wanted a fresh start. Ultimately, Mullah Fazlullah emerged as the third leader of the TTP. Fazlullah — a non-Mehsud who had no links to the tribal areas — led a brutal campaign in his hometown in Pakistan's Swat region in 2008 and 2009. He was known as "Mullah Radio" for using a pirate radio station to enforce and propagate hardline Islamic law.
"The TTP scattered once Fazlullah took over," Ashraf said, explaining that Fazlullah had no standing among the tribes that formed the Taliban's core movement. "This was always a clique, where standing and shared experience — fighting the Soviets and then the Americans — mattered."
Siddiqa disagreed with that assessment, arguing that the Pakistani Taliban and other armed groups "are all connected operationally." She said the recent massacre in Peshawar relied heavily on the "interconnectedness" of the various factions.
But, according to Abdullah, the military offensive in North Waziristan has impacted the TTP's "operational capabilities," and led to the formation of splinter groups.
"It's a bizarre situation," Abdullah said. "Fazlullah feels he has to assert his authority and be seen as something."
Ashraf, the counterterrorism expert, said the TTP is "losing members at an alarming rate" under Fazlullah's leadership.
The consensus among the experts is that Fazlullah's desperation for legitimacy has been amplified by the fact that he is fast losing support among members of the Afghan Taliban. This alliance is important because both groups view Mullah Omar — the Afghan Taliban leader — as a unified spiritual guide.
Abdullah said the Afghan Taliban's condemnation of the Peshawar attack was "very significant" and the first time the Afghans publicly denounced their Pakistani counterparts.
"The intentional killing of innocent people, women, and children goes against the principles of Islam," the Afghan Taliban's statement said.
'They're trying to distance themselves from Fazlullah and show backers in Pakistan that they're different," Abdullah said.
Power brokers in Islamabad, Pakistan's capital will likely decide what happens next in the conflict. Abdullah suggested the massacre in Peshawar was both an act of desperation by the Pakistani Taliban and the result of strategic decisions made by the Pakistani military to favor some militant groups while cracking down on others.
Siddiqa echoed that assessment, and said Pakistan's government must change its regional strategy and start treating all armed groups equally, with input from civilians about how to proceed.
"The strategy to deal with both the Afghan and the Pakistani Taliban as the exclusive domain of the Pakistan armed forces has backfired," Siddiqa said.
Barring such a change, Siddiqa concluded, there will be more violence in Pakistan.
Follow Ali Mustafa on Twitter: @Ali_Mustafa