From Adam Entous, Siobhan Gorman, and Margaret Coker, Wall Street Journal:  Nearly eight weeks after the attacks, a complete accounting hasn’t emerged in public view. The brunt of the public criticism for security lapses has so far been directed at the State Department, rather than the CIA, which, by design, operates largely in the shadows. Critics in Congress say the CIA has used secrecy in part to shield itself from blame—a charge officials close to the agency deny.

This account of the CIA presence in Benghazi sheds new light on the events, and how the essentially covert nature of the U.S. operations there created confusion. Congressional investigators say it appears that the CIA and State Department weren’t on the same page about their respective roles on security, underlining the rift between agencies over taking responsibility and raising questions about whether the security arrangement in Benghazi was flawed.

The CIA’s secret role helps explain why security appeared inadequate at the U.S. diplomatic facility. State Department officials believed that responsibility was set to be shouldered in part by CIA personnel in the city through a series of secret agreements that even some officials in Washington didn’t know about.

It also explains why the consulate was abandoned to looters for weeks afterward while U.S. efforts focused on securing the more important CIA quarters. Officials say it is unclear whether the militants knew about the CIA presence or stumbled upon the facility by following Americans there after the attack on the consulate. . . .

Protecting the CIA annex was a roughly 10-man security force. The State Department thought it had a formal agreement with the CIA that called for that force to be used in emergencies to bolster security for the consulate.

The State Department has been criticized by lawmakers and others for failing to provide adequate security for its ambassador, especially in light of an attack there in June and after other violence prompted the U.K. to pull out of the city. In October, Mrs. Clinton took responsibility for any security lapses.

Among U.S. diplomatic officials in Libya, the nearby CIA force and the secret agreement allayed concerns about security levels.

"They were the cavalry," a senior U.S. official said of the CIA team, adding that CIA’s backup security was an important factor in State’s decision to maintain a consulate there.

In the months leading up to the attack, Mr. Stevens and others sent a series of diplomatic messages to the administration warning that security in Benghazi was deteriorating. Nevertheless, security at the consulate wasn’t beefed up and Mr. Stevens’s movements weren’t restricted, according to congressional investigators.

On the night of the attack, the consulate, on a 13-acre property, was protected by five American diplomatic security officers inside the walls, supported by a small group of armed Libyans outside. The CIA’s security force at the annex sometimes provided backup security for the ambassador when he traveled outside the consulate.

Outside of Tripoli and Benghazi, the nature of the security relationship between the consulate and the annex wasn’t widely known, and details about that arrangement are still the subject of dispute. The night of the attack, many top officials at the State Department in Washington weren’t initially aware that the annex had a security force that answered to the CIA and provided backup security for the consulate. . . .

The emphasis on security at the CIA annex was underscored the day after the attack. With all U.S. personnel evacuated, the CIA appears to have dispatched local Libyan agents to the annex to destroy any sensitive documents and equipment there, even as the consulate compound remained unguarded and exposed to looters and curiosity seekers for weeks, officials said. Documents, including the ambassador’s journal, were taken from the consulate site, and the site proved of little value when Federal Bureau of Investigation agents finally arrived weeks later to investigate.

U.S. officials said they prioritized securing the annex because many more people worked there and they were doing sensitive work, while the consulate, by design, had no classified documents. The American contractor said the top priority was destroying sensitive documents.

In the aftermath of the assault, questions have been raised within the administration and on Capitol Hill about Mr. Petraeus’s role in responding to the attack. On Oct. 10, lawmakers grilled senior State Department officials about the attack. At one point, lawmakers and officials alluded for the first time to the existence of the CIA facility. That set off alarms at the agency and at the State Department because that information was classified. . . .

In ensuing weeks, tensions over the matter spread to the FBI and Capitol Hill. The FBI didn’t initially get to review surveillance footage taken at the compound because officials say it was being analyzed by the CIA. The CIA, in turn, wasn’t able to immediately get copies of FBI witness interviews, delaying the agency’s analysis of what happened outside the consulate and at the annex.

A senior congressional investigator said the secrecy has made it harder to figure out what errors were made, because classification restrictions have allowed the CIA to avoid public and congressional scrutiny for its conduct. Information about the CIA’s role has largely been limited to congressional intelligence committees, which are reviewing the attacks but have not launched investigations into them.  (graphic: AP)