CIA operatives who were the first boots on the ground behind Taliban lines after the Sept. 11 attacks say they feel betrayed by President Biden’s botched withdrawal from Afghanistan.

The author telling Team Alpha operatives’ story in his new book, “First Casualty: The Untold Story of the CIA Mission to Avenge 9/11,” Toby Harnden, told Fox News that former CIA officers are carrying a burden of sadness over the deadly withdrawal.

“There is a deep sense of sadness among former CIA officers about the desperate situation in Afghanistan and the return to power of the Taliban, a movement of medieval brutality,” Harnden said.

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“The consensus among the Team Alpha members is that the decision to withdraw U.S. forces completely was a mistake and that the evacuation of Kabul was catastrophically mismanaged,” he continued.

“As they were 20 years ago, the six living members of Team Alpha are focused on what they feel is their current mission – to get those who fought with them in 2001, and their families, out of Afghanistan before the Taliban slaughter them,” Harnden said in an email to Fox News.

“Some of the former officers are spending almost every waking hour fielding WhatsApp calls, receiving photos of documents, and compiling lists for evacuations by private companies and NGOs,” he continued.

Harnden added that Shannon Spann, the widow of the first post-9/11 American casualty, CIA paramilitary officer and former Marine officer Mike Spann, with whom she had three children and “herself a former CIA officer, has also been deeply involved in these rescue efforts.”

Harnden added in a phone interview on Wednesday that the surviving team members are active in the administrative side of the rescue efforts with some members still affiliated with the CIA being potentially more directly involved.

Harnden said his book chronicles the eight “elite warriors” of Team Alpha in their mission in October 2001, a month following the Sept. 11 attacks.

“[They were] different from the usual, kind of green, recruit types in their early 20s,” Harnden said, remarking that the group was over a decade older than the typical squad sent in. “These were some seasoned, seasoned people. They were sort of an eclectic bunch. They were sort of quirky.”

Harnden said the covert operation was “put together sort of on the fly” with a lot of improvisation and noted that the members of Team Alpha had never worked with each other before, having fought hard to get on the team amid fears of another attack.

In his book, Harnden tells the story of Mike Spann, who perished in a prison uprising in Afghanistan.

“Mike Spann’s comrade David Tyson, about 40 yards from the Pink House, was startled by the commotion,” Harnden writes in his book. “Time slowed down as his brain processed what his eyes and ears were telling him.”

“Weapons were being grabbed, grenades were exploding, and the area where Mike had been standing was a melee of bodies. David stared at the chaos, still not quite registering that this was a prisoner revolt. He drew his Browning pistol.”

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Spann was killed when he was overwhelmed by Afghan prisoners who overran him and turned his own weapon on him.

Houston Keene is a reporter for Fox News Digital. You can find him on Twitter at @HoustonKeene.