The NYT says it was a loosely planned attack, not by Al Qaeda, precipitated by the video
Fifteen months after Mr. Stevens’s death, the question of responsibility remains a searing issue in Washington, framed by two contradictory story lines.
One has it that the video, which was posted on YouTube, inspired spontaneous street protests that got out of hand. This version, based on early intelligence reports, was initially offered publicly by Susan E. Rice, who is now Mr. Obama’s national security adviser.
The other, favored by Republicans, holds that Mr. Stevens died in a carefully planned assault by Al Qaeda to mark the anniversary of its strike on the United States 11 years before. Republicans have accused the Obama administration of covering up evidence of Al Qaeda’s role to avoid undermining the president’s claim that the group has been decimated, in part because of the raid that killed Osama bin Laden.
The investigation by The Times shows that the reality in Benghazi was different, and murkier, than either of those story lines suggests. Benghazi was not infiltrated by Al Qaeda, but nonetheless contained grave local threats to American interests. The attack does not appear to have been meticulously planned, but neither was it spontaneous or without warning signs.
http://www.nytimes.com/projects/2013/benghazi/?ref=world#/?chapt=0