(J. Scott Applewhite/ASSOCIATED PRESS)

Last fall, nearly a year after a suicide bomber managed to kill seven CIA operatives at their base in eastern Afghanistan, the agency disclosed an overview of its findings into exactly how the disaster had been allowed to happen.

Yes, warning signs had been missed. Yes, there had been certain systemic breakdowns in judgment. Yes, security procedures would be tightened.

The findings, while damning, seemed somehow like standard fare in a city full of inspectors general and oversight committees. The investigation did not assign blame to any individual or department within the agency.

Now comes a far more revealing look at what led up to that bombing, the deadliest single incident for the CIA in 25 years.

In “The Triple Agent: The al-Qaeda Mole who Infiltrated the CIA,” a new book by our colleague Joby Warrick, we learn that a veteran CIA case officer wrote at least two internal memos expressing concern about Humam al-Balawi, the 32-year-old suicide bomber who succeeded in penetrating the agency’s base in Khost.

Darren LaBonte, who was among those killed in the bombing, argued that the CIA didn’t know enough about Balawi to trust him, despite the Jordanian’s claims that he could deliver Ayman al-Zawahiri, then al-Qaeda’s No. 2. LaBonte also argued that the plans to take in Balawi – 14 intelligence operatives and a driver had been assigned to the debriefing – put too many individuals at risk.

“It’s a gaggle,” he said after a CIA team rehearsed their plans in late December 2009, according to Warrick’s account.

LaBonte’s memos were far from the only warning signs that went unheeded. In another one of the most glaring oversights in the case, a CIA officer dismissed the concerns of a senior Jordanian intelligence operative who feared the agency was being set up for an ambush. The officer who received the warning thought it was just part of a turf war among the Jordanians over who should handle the case. Dane Clark Paresi, a security contractor at the base, also complained to supervisors about arrangements ahead of Balawi’s visit.

The CIA spent untold hours discussing the Balawi case, and planning for best how to use him as an asset. And it wasn’t just the agency. Top members of the Obama administration’s national security team at the time, including national security adviser James L. Jones, Director of National Intelligence Dennis C. Blair, and Obama’s chief of staff, Rahm Emanuel, were all briefed.

“Perhaps two dozen people in the world knew about the pending visit by Human al-Balawi, but one of them happened to reside at 1600 Pennsylvania Avenue in Washington,” Warrick writes. “President Barack Obama, in his second briefing about Jordan’s ‘golden source,’ had been told of CIA plans to meet with the informant in Afghanistan.”

Ultimately none of the preparations and debriefs was enough to prevent Balawi’s plan from succeeding. As Warrick writes: The warning signs were obscured by the eagerness of “war-weary intelligence operatives” who “saw a mirage and desperately wanted it to be real.”

“The Triple Agent” is full of other revealing nuggets about the bombing at Khost, and about U.S. counterterrorism operations in general. Among the highlights:

— U.S. officials became gravely worried in the spring of 2009 about a possible dirty-bomb threat that surfaced in Pakistan’s tribal belt. Intelligence intercepts picked up a discussion among members of the Pakistani Taliban about the possible use of a “nuclear device” that was controlled by militants loyal to then-Taliban chief Baitullah Mehsud. The intercepts prompted a wide search and led to high-level meetings between U.S. and Pakistani officials, as well as increased pressure to find and kill Mehsud. The Taliban official was killed weeks later in a drone strike. The bomb-scare was never made public, and no evidence was ever found confirming that such a device truly existed.

— The CIA unleashed waves of retaliatory attacks against al-Qaeda and Taliban targets after the suicide bombing at Khost, and in one of the strikes it achieved a measure of poetic justice. On May 21, 2009, a Predator drone fired missiles at a compound in the Pakistan’s tribal region, killing Sheikh Saeed al-Masri, al-Qaeda’s operations chief at the time of the Khost bombing. Coincidentally, on the same day, Elizabeth C. Hanson, a CIA officer and the last of the seven U.S. victims of the attack, was buried at Arlington National Cemetery. Panetta and his aides were coordinating arrangements for the strike as the services were underway, and the missiles were fired shortly after Hanson’s remains were lowered into the ground.

— During Obama’s Afghanistan-Pakistan strategy review in 2009, CIA Director Leon Panetta presented the White House with a “wish list” of what it needed to succeed. The most crucial request was one for more armed drones to help target al-Qaeda leader and carry out “the most aggressive operation in the agency’s history.” On the day Panetta made his case, Obama turned to his aides and said: “We’re going to do what Leon wants.”