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…

In Libya, the relationship between the State Department and CIA was secret and symbiotic: The consulate provided diplomatic cover for the classified CIA operations. The State Department believed it had a formal agreement with the CIA to provide backup security, although a congressional investigator said it now appears the CIA didn’t have the same understanding about its security responsibilities…

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…

“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.