Here's a look at what you need to know about the September 11, 2012, attack on the U.S. mission in Benghazi, Libya.
September 11, 2012 - The U.S. mission in Benghazi, Libya, is attacked and burned. An attack later that night involves mortar and rocket fire against a U.S. diplomatic annex in the city.
U.S. Ambassador Christopher Stevens and three other U.S. nationals are killed in the attack.
More than 30 Americans are evacuated.
Initially, the attack was thought to be perpetrated by an angry mob responding to a video made in the U.S. which mocked Islam and the Prophet Mohammed, but it is later determined to be a terrorist attack.
September 11-12, 2012 Attack Timeline as released by the Pentagon:
September 11: (Events listed in local Benghazi time)
9:42 pm - Armed men begin their assault on the U.S. mission.
9:59 pm - A surveillance drone is directed to fly over the U.S. compound, but it is unarmed.
10:32 pm - The Office of the Secretary Defense and the Joint Staff are notified of the attack by the National Military Command Center at the Pentagon. "The information is quickly passed to Secretary Leon Panetta and General Dempsey."
11 pm - Secretary Panetta and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey meet with President Barack Obama at the White House where they discuss the unfolding situation and how to respond. The meeting had been previously scheduled.
11:10 pm - The surveillance drone arrives over the Benghazi facility.
11:30 pm - All surviving U.S. personnel are evacuated from the mission. U.S. Ambassador Chris Stevens and State Department computer expert Sean Smith are killed in the initial assault.
Midnight to 2 am - Secretary Panetta and other senior leaders discuss possible options for further violence if it were to break out. Panetta gives verbal orders for Marine anti-terrorist teams from Rota, Spain, to prepare to deploy to Tripoli and Benghazi. Panetta also orders a special operations force team training in Croatia and an additional special operations force team in the United States to prepare to deploy to a staging base in southern Italy.
1:30 am - A six-man security team from the U.S. Embassy in Tripoli arrives in Benghazi.
2:39 am to 2:53 am - The National Military Command Center gives formal authorization for the deployment of the two special operations force teams from Croatia and the United States.
5:15 am - Attackers launch assault on a second U.S. facility in Benghazi. Two former U.S. Navy SEALs acting as security contractors are killed. They are identified as Tyrone Woods and Glen Doherty.
6:05 am - A C-17 aircraft in Germany is told to prepare to deploy to Libya to evacuate the mission personnel.
7:40 am - The first wave of Americans are evacuated to Tripoli via airplane.
10 am - A second group, including those killed in the attack, are flown to Tripoli.
2:15 pm - The C-17 departs from Germany for the flight to Tripoli.
7:17 pm - The C-17 leaves Tripoli with the American mission personnel and the bodies of Stevens, Smith, Woods and Doherty.
7:57 pm - The U.S. special operations force team based in Croatia arrives at a staging base in Italy.
8:56 pm - One of the Marine anti-terrorist teams from Spain arrives in Tripoli.
9:28 pm - The U.S.-based special operations force team arrives at its staging base in Italy.
September 11, 2012 - Initial reports claim a mob of angry protestors gather outside the U.S. temporary mission in Benghazi, Libya. Protestors reportedly storm the building, and Ambassador Stevens dies of smoke inhalation as does IT expert Sean Smith. Two security personnel, former U.S. Navy Seals Glen Doherty and Tyrone Woods, are killed in a subsequent attack after helping to evacuate those at the mission to a US diplomatic annex.
September 11, 2012 - Republican presidential candidate Mitt Romney releases a statement at about 10:30 p.m. ET, "I'm outraged by the attacks on American diplomatic missions in Libya and Egypt and by the death of an American mission worker in Benghazi. It's disgraceful that the Obama administration's first response was not to condemn the attacks on our diplomatic missions, but to sympathize with those who waged the attacks." This was in response to the U.S. Embassy in Cairo releasing a statement denouncing the film, "Innocence of Muslims," that had led to the protests. Later it emerges that the statement preceded the protests.
September 12, 2012 - In an address from the Rose Garden, President Barack Obama says "The United States condemns in the strongest terms this outrageous and shocking attack. ... no acts of terror will ever shake the resolve of this great nation." Later that day he says, "No act of terror will dim the light of the values that we proudly shine on the rest of the world, and no act of violence will shake the resolve of the United States of America."
September 13, 2012 - At a campaign stop in Golden, Colorado, President Obama says, "I want people around the world to hear me: To all those who would do us harm, no act of terror will go unpunished."
September 13, 2012 - Doubts about the cause of the attack pick up steam. A senior U.S. official tells CNN, "The video or 9/11 [anniversary] made a handy excuse and could be fortuitous from their perspective, but this was a clearly planned military-type attack."
September 14, 2012 - President Barack Obama and Secretary of State Hillary Clinton attend a funeral service for the four victims at Joint Base Andrews, Maryland.
September 14, 2012 - CNN reporters find a journal belonging to Ambassador Stevens on the floor of the mission compound. They use relevant information from the journal for reporting and return it to his family.
September 16, 2012 - U.S. Ambassador to the United Nations Susan Rice says, "We do not have information at present that leads us to conclude that this was premeditated or preplanned" and "Soon after that spontaneous protest began outside of our mission in Benghazi, we believe that it looks like extremist elements, individuals, joined in that in that effort..."
September 19, 2012 - Matthew Olsen, director of the National Counterterrorism Center, tells the Senate Homeland Security and Governmental Affairs Committee that the ambassador and three other Americans "were killed in the course of a terrorist attack on our embassy." This is the first time an Obama administration official uses the term "terrorist attack" to describe what happened.
September 20, 2012 - After days of repeating that the video mocking Islam caused the attack, White House Press Secretary Jay Carney says: "It is, I think, self-evident that what happened in Benghazi was a terrorist attack. Our embassy was attacked violently, and the result was four deaths of American officials." U.S. officials also back away from the theory that a protest led to the attack.
September 21, 2012 - Secretary of State Hillary Clinton says, "What happened in Benghazi was a terrorist attack, and we will not rest until we have tracked down and brought to justice the terrorists who murdered four Americans."
September 25, 2012 - President Obama says on ABC's "The View" in response to whether the attack was an act of terrorism: "We're still doing an investigation. There's no doubt that (with) the kind of weapons that were used, the ongoing assault, that it wasn't just a mob action. We don't have all the information yet and so we're still gathering it."
September 27, 2012 - Secretary Panetta says, "As we determined the details of what took place there and how that attack took place, that it became clear that there were terrorists who had planned that attack...."
October 1, 2012 - Representative Peter King (R-NY), demands that U.S. Ambassador Susan Rice step down after making what he called misleading comments about the attack in Benghazi.
October 4, 2012 - An FBI team arrives at the mission to investigate. They are delayed nearly three weeks because of security concerns.
October 9, 2012 - Two senior State Department officials brief reporters saying there was no prior indication that an attack was imminent, there was "nothing unusual" throughout the day of the attack, and that Ambassador Stevens held a meeting with a Turkish diplomat that evening and then retired to his room in one of the compound's buildings at 9 p.m.
October 9, 2012 - CNN reports that Eric Nordstrom, regional security officer in Libya until July 2012 sent two diplomatic cables to the state Department requesting additional security agents for the Benghazi mission. The cables were sent in March and July 2012.
October 15, 2012 - Secretary Clinton says, "I take responsibility. I'm in charge of the State Department's 60,000-plus people all over the world, 275 posts."
October 16, 2012 - During a presidential debate, President Obama says: "I am ultimately responsible for what's taking place there because these are my folks, and I'm the one who has to greet those coffins when they come home."
October 19, 2012 - Several senior administration officials tell CNN that UN Ambassador Susan Rice's use of the word "spontaneous" to describe the Benghazi attack came directly from an assessment provided by the CIA, which was not edited by the White House. This assessment is revised following Ambassador Rice's use of the word.
October 25, 2012 - The Senate Select Committee on Intelligence announces it will hold hearings to review the attack.
November 3, 2012 - A U.S. government official tells CNN that the FBI is expected to question Ali Ani al Harzi, a suspect in the mission attack. The United States first became aware of Ali Ani al Harzi when he apparently posted details of the attack on social media while it was happening. He was detained by Turkish officials after he crossed into the country from Libya.
November 8, 2012 - Mark Basseley Youssef (the Egyptian-American film maker who made "Innocence of Muslims" which was originally blamed for the mission attack) is sentenced to one year in federal prison for violating the terms of his probation from a 2010 bank fraud case. He is also ordered to serve four years of supervised release after his prison term.
November 15, 2012 - The Senate Select Committee on Intelligence holds a closed oversight hearing.
December 18, 2012 - An independent review of the September 11 attacks on the U.S. mission in Benghazi is released. The report cites "systemic failures and leadership and management deficiencies" at the State Department.
January 23, 2013 - Secretary Clinton testifies for more than five hours before the House Foreign Affairs Committee and the Senate Foreign Relations Committee. Clinton acknowledges a "systemic breakdown" as cited by an Accountability Review Board but says that her department is taking additional steps to increase security at U.S. diplomatic facilities.
April 23, 2013 - House Republican leaders release a 46-page interim progress report about the terror attack in Benghazi, in which they claim former Secretary of State Hillary Clinton personally signed off on cuts in security at the compound, which they say would contradict her congressional testimony.
May 4, 2013 - A senior Republican releases names of witnesses for a May 8, 2013, congressional hearing on the attack, including two characterized by Republicans as whistleblowers. The witnesses include Mark Thompson, the acting deputy assistant secretary for counterterrorism; Gregory Hicks, a foreign service officer and former deputy chief of mission/chargé d'affairs in Libya; and Eric Nordstrom, diplomatic security officer and former regional security officer in Libya.
May 8, 2013 - Testimony is given at a six-hour Republican-led House Oversight Committee hearing from State Department whistleblowers who had not previously testified, including details from Gregory Hicks who was on the ground in Tripoli at the time of the attack.
May 9, 2013 - Committee members request additional hearings and the release of unclassified emails that preceded the initial statements given to the public by U.S. Ambassador to the United Nations Susan Rice.
May 15, 2013 - The White House releases more than 100 pages of e-mails detailing the development of unclassified talking points used to explain the events of last September 11. CNN reports, "The e-mails indicate the CIA was likely the lead organization in developing the talking points, with the State Department recommending significant changes."
August 7, 2013 - Federal authorities file the first criminal charges and several suspects including prominent Libyan militia figure Ahmed Abu Khattalah are charged in the Benghazi mission attack.
November 13-14, 2013 - CIA contract security officers who initially responded to the Benghazi mission attack appear before a House Intelligence subcommittee. The sessions take place behind closed doors, but a congressional source tells CNN that the CIA contract operatives testified they were told by the CIA to sign nondisclosure agreements just before a memorial ceremony at the CIA's headquarters in Langley, Virginia, this past May. Their testimony seems to contradict information sent by CIA Director John Brennan to the House Intelligence Committee investigating the events in Benghazi.
November 15, 2013 - The U.S. State Department discloses for the first time that a reward of up to $10 million is being offered for information leading to the arrest of anyone involved in the Benghazi mission attack. Though charges have been filed regarding the case, no one has been arrested. The reward has been in effect since January but never publicized.
January 15, 2014 - The Senate Intelligence Committee releases a report on Benghazi. The report states that the majority of the committee believe that attack was "likely preventable" based on known security shortfalls at the facility and prior warnings.
May 2, 2014 - House Speaker John Boehner announces that he will form a select committee to investigate the 2012 Benghazi terror attack. The move comes after previously unreleased documents, including an email from a White House national security aide, add to questions about what the Obama administration knew about the armed assault and how it responded in the days after.
June 17, 2014 - U.S. officials announce that U.S. forces working with the FBI have captured a key suspect, militia leader Ahmed Abu Khatallah, in the attack on the American diplomatic compound in Benghazi. He is currently being held aboard the USS New York on his way to the United States.
June 28, 2014 - Khatallah appears before a judge in Washington, DC, to plead not guilty to one count of providing material support to terrorists.
November 21, 2014 - The U.S. House of Representatives Permanent Select Committee on Intelligence releases a report on the Benghazi attacks. The report concludes there was no intelligence failure prior to the attack, no stand-down order to CIA operatives trying to go assist at the besieged consular building and found conflicting intelligence in the wake of the attack about the motive and cause, which were reflected in early public comments by the Obama administration.