Ambassador Chris Stevens, State Department information officer Sean Smith, and embassy security workers Glen Doherty and Tyrone Woods -- both former Navy SEALs -- were killed in a Sept. 11 firefight that followed protests at the mission initially publicly ascribed to Muslim anger at a film produced in Southern California that defamed the Prophet Muhammad, the founder of Islam.
The attack in Benghazi came after protesters in Cairo had torn down an American flag at the U.S. Embassy and replaced it with an al-Qaida flag, but the State Department initially indicated it could not confirm whether the Benghazi attack was related to the Cairo incident.
Speaking at the White House the day after the attack, President Barack Obama said "no acts of terror will ever shake the resolve of this great nation." White House spokesman Jay Carney maintained for several days there was no evidence to indicate the attack was "planned or imminent."
Conservative media began almost immediately to focus on the question of whether the attack was planned or spontaneous, and whether the administration was misrepresenting it to the public. Eventually, the question began to receive wider coverage and Benghazi became an issue in the presidential campaign.
Congressional Republicans placed particular emphasis on public comments by U.N. Ambassador Susan Rice, who said on ABC's "This Week" six days after the attack, the protest in Benghazi "seems to have been hijacked, let us say, by some individual clusters of extremists who came with heavier weapons, weapons that as you know in -- in the wake of the revolution in Libya ... are quite common and accessible."
Appearing the same day on CBS' "Face the Nation," U.S. Sen. John McCain, R-Ariz., said there was no doubt the attack "was an act of terror."
Congressional Republicans said in early October the Benghazi facility had been threatened and attacked 13 times and the Sept. 11 attack "was clearly never, as administration officials once insisted, the result of a popular protest."
In a letter to Secretary of State Hillary Clinton, Reps. Darrell Issa of California and Jason Chaffetz of Utah -- both Republicans -- said U.S. officials had confirmed that, "prior to the Sept. 11 attack, the U.S. mission in Libya made repeated requests for increased security in Benghazi. The mission in Libya, however, was denied these resources by officials in Washington."
Issa, chairman of the House Oversight and Government Reform Committee, opened hearings on the attack Oct. 10.
Republican presidential nominee Mitt Romney said the attack was a sign Obama's foreign policy was "unraveling."
During their second presidential debate, Obama accused Romney of trying to make political hay out of the deaths of four Americans, and said he found it "offensive" to suggest he or anyone in his administration would "play politics" or mislead about what happened in Benghazi.
At one point during the debate, Romney said Obama had declined to call the attack an actor of terror but -- in an iconic moment of the 2012 campaign -- he was corrected by moderator Candy Crowley, the host of CNN's "State of the Union."
"He -- he did call it an act of terror," Crowley told Romney.
By the third week of October, U.S. officials whose names were not reported were telling news organizations there was no evidence the attack was planned "days or weeks in advance."
McCain, joined by fellow Senate Republicans Lindsey Graham of South Carolina, Kelly Ayotte of New Hampshire and Ron Johnson of Wisconsin, wrote to Obama at the end of October saying there was a "growing perception among many of our constituents that your administration has undertaken a concerted effort to misrepresent the facts and stonewall Congress and the American people."
In early November senior U.S. intelligence officials said the CIA, not the State Department, was the commanding agency at Benghazi mission. They said Woods and Doherty were contracted by CIA and had been part of a team that provides security to CIA case officers.
After CIA Director David Petraeus resigned Nov. 9, citing an extramarital affair, Obama critics suggested the resignation was meant to allow Petraeus to avoid testifying in closed-door congressional hearings about the Benghazi assault but Petraeus testified as scheduled.
A central question about the talking points Rice was using as a basis for her public comments was whether the White House had revised points provided by intelligence officials, but a spokesman for the Director of National Intelligence eventually said unclassified talking points used by government officials who spoke about the attack were not substantively changed by any agency outside the intelligence community.
In his first news conference following his re-election, Obama was visibly upset with McCain and Graham for accusing Rice of trying to mislead the public.
"She made an appearance [on Sunday TV talk shows] at the request of the White House, in which she gave her best understanding of the intelligence provided to her," he said. "If Senator McCain and Senator Graham and others want to go after somebody, they should go after me."
"Mr. President, don't think for one minute I don't hold you ultimately responsible for Benghazi," Graham said in response. "I think you failed as commander in chief before, during and after the attack."
Senate Majority Leader Harry Reid, D-Nev., said he opposed a resolution by McCain, Graham and Ayotte to create a special Senate committee to investigate the attack.
Following a classified briefing for members of Congress, Sen. Joe Lieberman, Ind.-Conn., said the Senate Homeland Security and Governmental Affairs Committee can handle an investigation and the committee's top Republican, Susan Collins of Maine, concurred.
After meeting with Rice in late November, McCain, Graham and Ayotte said they had even graver doubts about her handling of the matter.
"Bottom line, I'm more disturbed now than I was before [by] the 16 September explanation about how Americans died in Benghazi, Libya, by Ambassador Rice," Graham said.
Ayotte said she would block any secretary of state nominee "until we get sufficient information" on the Benghazi matter.
"Before anyone can make an intelligent decision about promoting someone involved in Benghazi, we need to go look through a lot more," Graham said.
Rice withdrew her name from consideration as secretary of state Dec. 13, telling Obama in a letter "the confirmation process would be lengthy, disruptive, and costly -- to you and to our most pressing national and international priorities. That trade-off is simply not worth it to our country."
"While I deeply regret the unfair and misleading attacks on Susan Rice in recent weeks, her decision demonstrates the strength of her character, and an admirable commitment to rise above the politics of the moment to put our national interests first," Obama said.
An independent review of the Benghazi attack -- congressionally mandated in cases involving the killing of Americans working for the U.S. government are killed overseas -- found there were "systemic failures and leadership and management deficiencies" at the State Department, that the mission was "severely under-resourced with regard to certain needed security equipment" and there needs to be "a more serious and sustained commitment from Congress to support State Department needs."
The review board concluded the security plan for the Benghazi facility was "grossly inadequate to deal with the attack that took place."
Clinton notified congressional leaders she endorsed every one of the review board's recommendations.
The board said there was no evidence of misconduct on the part of any U.S. government employees.