Mandel Ngan / AFP - Getty Images

A June 23, 2011, file photo shows Paula Broadwell, second from left, watching as Gen. David Petraeus and his wife, Holly Petraeus arrive for a Senate Select Intelligence Committee hearing on Petraeus' nomination to be director of the Central Intelligence Agency.

What began with David Petraeus’ surprise resignation as CIA director on Friday resulting from an extramarital affair has now spiraled into a complicated story of infidelity, intrigue and politics.

Petraeus’ admission of an extramarital affair quickly led to his biographer, Paula Broadwell, and an examination of her relationship with the decorated war hero. The length of the FBI’s investigation of “menacing” emails sent to Petraeus’ family friend Jill Kelley, and the timing of the announcement of his departure from the Obama administration fueled conspiracy theories. Then Gen. John Allen, Petraeus’ successor as military commander in Afghanistan, was embroiled in the scandal, accused by U.S. officials of sending “inappropriate” emails to Kelley.

To help you keep the facts straight, NBC News has compiled this timeline, based on reporting by NBC News and other published accounts:

Spring 2006 -- Paula Broadwell meets Gen. David Petraeus, when she introduces herself after he gave a speech at Harvard's Kennedy School, where Broadwell was working on a master's degree, the Wall Street Journal reported. 

October 2008 -- Petraeus takes over as head of U.S. Central Command, based at MacDill Air Force Base. While serving there, he reportedly meets Jill Kelley and her husband, Dr. Scott Kelley. She is described in various accounts as a volunteer “social liaison” between the community and the base.

2008 -- Broadwell begins her doctoral dissertation, "a case study of General Petraeus’ leadership," according to Rolling Stone magazine.  

June 2009 -- Broadwell and her husband, Scott, purchase a home in Charlotte, N.C., the Charlotte Observer reports. 

June 2010 -- Petraeus is named as replacement for Gen. Stanley McChrystal as the top commander in Afghanistan after the latter makes impolitic remarks to a Rolling Stone reporter. Broadwell decides to turn her dissertation into a book.  

July 2010-July 2011 – According to an online biography of Broadwell that was taken down after Petraeus’ resignation, she made multiple trips to Afghanistan during this period, where she “embedded with the general, his headquarters staff and his soldiers on the front lines of fighting across Afghanistan to chronicle the experiences of this American general as they are brought to bear in the terrible crucible of war.”  

Aug. 31, 2011 -- Petraeus retires from the U.S. Army, departs Afghanistan.

Sept. 6, 2011 -- Petraeus takes over as director of the CIA.

Early November 2011 – According to former Petraeus spokesman Steve Boylan, who had spoken to his former boss after his resignation, Petraeus' affair with  Broadwell began around this time, approximately two months after he took the CIA job.  

January 2012 – “All In, The Education of General David Petraeus,” by Paula Broadwell with Vernon Loeb is published by Penguin Press.

May 2012 – “Menacing” emails – five to 10 of them, according to the Wall Street Journal -- began arriving in Jill Kelley's inbox, NBC’s Michael Isikoff and Pete Williams report. 

Emails on 'comings and goings' of Petraeus, other military officials escalated FBI concerns

June 2012 – The FBI investigation begins. A source close to Kelley tells Isikoff that she took the emails, which she viewed as harassing or menacing, to the FBI. The source said the anonymous emails didn’t mention Petraeus by name, but subsequent emails – sent from multiple alias accounts -- contained references to the "comings and goings" of high-level military officials -- including events that were not on any public schedule. This raised the question as to whether somebody had access to sensitive -- and classified -- information about the CIA director. 

T.Ortega Gaines / Charlotte Observer via Reuters

Paula Broadwell is pictured before embarking on a national book tour to promote "All In," her biography of Gen. David Petraeus.

July 2012 – Approximate end of the affair between Broadwell and Petraeus, according to former Petraeus spokesman Steve Boylan, who  tells NBC’s Kristen Welker in early November that it ended “about four months ago.” 

Late  summer -- Attorney General Eric Holder is told that agents have discovered an email link between Petraeus and Broadwell, which included exchange of “explicit details of a sexual nature,” according to the Wall Street Journal. 

September – FBI agents interview Paula Broadwell for first time, NBC’s Pete Williams reports.

Oct. 27  -- House Majority Leader Eric Cantor speaks to an FBI agent who had worked on the Petraeus investigation, according to Cantor spokesman Doug Heye. The agent-- who had originally contacted Rep. Dave Reichert, a Republican from Washington -- raised concerns that "sensitive information" relating to Petraeus may have been "compromised," Heye said. The timing of the tip to Reichert is not clear.

Week of Oct. 29 – FBI agents interview Petraeus and Broadwell (for a second time), according to NBC’s Michael Isikoff.

Approximately Oct. 30-31 – Somewhere around this time frame, Petraeus traveled to Tripoli to conduct his own personal inquiry into Benghazi, according to author Bob Woodward, appearing on "Meet the Press" on Nov. 11. NBC’s Andrea Mitchell confirmed that Petraeus had recently traveled to Libya.

Oct. 31 – After conferring with his chief of staff, Steve Stombres, and Richard Cullen, a former attorney general of Virginia, Cantor had Stombres call the FBI chief of staff to relay the information he had received from the FBI agent, NBC News has reported.

Nov. 1 -- Cantor aide Steve Stombres is told by the FBI that it cannot confirm or deny an investigation, but the bureau official assured the leader's office it was acting to protect national security.

Nov. 2 – The FBI concludes its investigation, according to NBC News’ Michael Isikoff, citing senior U.S. law enforcement official; the  last FBI interviews with both Broadwell and Petraeus also took place this day, NBC’s  Pete Williams reports, citing federal officials.

Nov. 6 – Justice Department informs Director of National Intelligence James Clapper.

Nov. 7 – Clapper informs the White House.

Nov. 8 –  Petraeus calls White House Deputy Chief of Staff Thomas Donilon and asks to see the president, NBC’s Andrea Mitchell reports. The White House tells Obama of the FBI investigation of Petraeus and his admission of an extramarital affair.

Nov. 9 – Obama accepts Petraeus’ resignation; Senate and House leaders first learn of it from media calls. They then speak to Petraeus, but don’t hear directly from the president, Mitchell reported.

Nov. 11 – Jill Kelley and her husband, Scott, issue statement: "We and our family have been friends with Gen. Petraeus and his family for over five years. We respect his and his family's privacy and want the same for us and our three children."

Afghanistan military commander Gen. John Allen investigated for 'inappropriate' emails

Chuck Burton / AP

FBI agents carry boxes and a computer from the home of Paula Broadwell in Charlotte, N.C.

Nov. 12 – In a surprise statement during a trip to Australia, Defense Secretary Leon Panetta announces that U.S. General John Allen, who succeeded Petraeus as military commander in Afghanistan, is under investigation over allegations he exchanged “inappropriate” emails with Kelley, the woman who triggered the investigation of Petraeus. Meanwhile, FBI agents carry out a four-hour “consensual search” of Broadwell’s home in Charlotte, N.C., leaving with eight to 10 cardboard boxes.

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