An anonymous email sent in May set off an elaborate chain of events that led to the downfall of former CIA Director David Petraeus, ensnared the top Afghan war chief and saw the Pentagon order a review of ethics training for senior officers. Lawmakers are demanding answers about who knew what and when. Here's a timeline of the scandal, according to officials involved in the investigation:
Spring 2006 — Paula Broadwell meets Petraeus at Harvard University, where she is a graduate student. Petraeus is a lieutenant general working on a counterinsurgency manual and is invited to speak about his experiences in Iraq.
January 2007 — The Senate confirms Petraeus as the commanding general for U.S. troops in Iraq.
2008 — Broadwell starts studying Petraeus' leadership. On a visit to Washington, Petraeus invites Broadwell to join him and his team for a run along the Potomac River.
October 2008 — Petraeus is named commander of U.S. Central Command, based at MacDill Air Force Base near Tampa, Fla., where socialite Jill Kelley and her husband attend events alongside the area's military elite.
June 30, 2010 — The Senate confirms Petraeus as the new commander for war in Afghanistan. Over the next year, Broadwell expands her research of Petraeus into an authorized biography. She makes multiple trips to Afghanistan and is given unprecedented access to Petraeus and his commanders.
Sept. 6, 2011 — Petraeus is sworn in as CIA director with his wife, Holly, by his side. Broadwell keeps in contact with Petraeus and is later invited to his office for events, including a meeting with actress Angelina Jolie.
Fall 2011 — Tampa socialite Jill Kelley attends an FBI "Citizens' Academy" in Florida, where Frederick W. Humphries, a veteran FBI counterterrorism investigator, gives a lecture.
November 2011 — Petraeus begins an extramarital affair with Broadwell, according to retired Army Col. Steve Boylan.
January 2012 — Broadwell's biography, "All In: The Education of General David Petraeus," is released. In an interview with her hometown paper, the Bismarck Tribune, Broadwell describes Petraeus as an inspirational figure who always takes care of his subordinates.
May 2012 — An anonymous email, ultimately traced to Broadwell, is sent to Gen. John Allen, the top U.S. commander in Afghanistan, warning him to stay away from Kelley, the Florida socialite. The email comes from the pseudonym "Kelleypatrol," and notes Allen's plans to see Kelley in Washington the following week. Confused about how anyone else would know about his personal plans, Allen forwards it to Kelley to see whether she's playing a prank on him.
Early June 2012 — Kelley starts receiving the first of several emails from various email accounts claiming she's up to no good. One email mentions Petraeus and an upcoming social event in Washington.
June 2012 — Kelley triggers an FBI investigation by showing the emails to Humphries, the FBI agent, who is concerned that the sender of the emails is tracking the movements of Allen and Petraeus.
July 2012 — The affair between Petraeus and Broadwell ends, according to Petraeus' friend Boylan. The anonymous emails to Kelley stop. The FBI designates the case a sensitive investigative matter, a designation that requires that FBI headquarters and Justice Department officials to be notified within 30 days.
August 2012 — Humphries tells Kelley he's been removed from the case and complains that the FBI is moving too slowly. Meanwhile, another FBI agent involved in the investigations tells Kelley the FBI has traced the emails to Broadwell, whom Kelley has never met.
Summer 2012 — Emails between Petraeus and Broadwell lead agents to believe the two are having an affair. FBI Director Robert Mueller is notified. At some point during the investigation, the FBI interviews Petraeus and Broadwell.
Late Summer 2012 — Attorney General Eric Holder is notified. By this time, the FBI has long since concluded there was no national security breach, but continues investigating whether Petraeus had any role in the harassing emails sent to Kelley.
Oct. 27 — Humphries calls House Majority Leader Eric Cantor and says he's worried the FBI isn't aggressively pursuing a possible security breach. Word of Humphries concerns first reaches Rep. Dave Reichert, R-Wash., who arranges for Humphries to speak with Cantor.
The week of Oct. 29 — Petraeus is interviewed for a second time by the FBI. By this point he has acknowledged the affair to the FBI.
Oct. 31 — Cantor's chief of staff calls the FBI chief of staff to inform him of the tip. Cantor is assured soon after that the FBI is on top of any possible vulnerability.
Friday, Nov. 2 — The FBI conducts what Attorney General Eric Holder later calls "a very critical interview" with Broadwell that convinces the Justice Department it knows enough about the case to inform the White House. In its final interview with Broadwell, the FBI learns how many classified documents she received and that none of them came from Petraeus.
Tuesday, Nov. 6 — As Americans cast their ballots on Election Day, the Justice Department informs Director of National Intelligence James Clapper of the investigation. Clapper calls Petraeus and urges him to resign.
Wednesday, Nov. 7 — The White House is first notified about the affair involving Petraeus. The retired general turns 60.
Thursday, Nov. 8 — President Barack Obama, having returned from Chicago, is told of the affair. Petraeus meets with Obama at the White House and asks to resign.
Friday, Nov. 9 — Obama accepts Petraeus' resignation. News of the resignation breaks before Congress is briefed. Broadwell's husband emails guests to cancel her 40th birthday party, scheduled for that weekend. By the evening, Broadwell has been publicly identified.
Sunday, Nov. 11 — Lawmakers complain in televised interviews that the FBI didn't alert them sooner to the investigation. Kelley's identity is revealed by The Associated Press, and she issues a statement asking for privacy.
Monday, Nov. 12 — The FBI searches Broadwell's house in Charlotte, N.C., with her consent. As she has told them to expect, the agents find classified documents there. The Pentagon orders an investigation into the Allen matter.
Tuesday, Nov. 13 — Pentagon reveals that Allen is under internal investigation for thousands of "inappropriate communications" with Kelley over a two-year period, and puts on hold his nomination to be the next commander of U.S. European Command and the commander of NATO forces in Europe. Macdill Air Force Base revokes Kelley's access pass.
Wednesday, Nov. 14 — President Barack Obama says he has seen no evidence that national security was threatened by the scandal. FBI Director Robert Mueller and Acting CIA Director Michael Morell meet privately with top lawmakers on intelligence committees. Defense Secretary Leon Panetta, traveling abroad, says he's confident Allen can continue to lead. Broadwell's security clearance is suspended.
Thursday, Nov. 15 — Citing a string of ethical lapses by senior military officers, Panetta orders a review of ethics training. The CIA opens an "exploratory" investigation into Petraeus' general conduct. Petraeus says in a CNN interview that he never gave classified information to Broadwell. Questioning continues on Capitol Hill, with Petraeus set to testify Friday about Libya before the House Intelligence Committee.
Associated Press writers Adam Goldman, Pete Yost, Michael J. Sniffen, Kimberly Dozier, Eileen Sullivan, Donna Cassata and Robert Burns contributed to this report.