Updated Saturday, November 10, 2012 at 02:23 PM
WASHINGTON — CIA Director David Petraeus abruptly resigned Friday after admitting to an extramarital affair in a shocking end to a career in which he rose to become the Army's leading counterinsurgency strategist, the top U.S. commander in Iraq and Afghanistan and then head of the country's premier spy agency.
The affair came to light as part of an FBI investigation into a potential security breach involving Petraeus' emails, according to federal law-enforcement officials and a former senior intelligence official.
The investigation uncovered emails describing an affair between Petraeus and Paula Broadwell, a former military officer and co-author of a glowing biography of Petraeus, according to two law-enforcement officials briefed on the investigation.
It remained unclear when the investigation began, how it evolved into an examination of Petraeus and whether it was continuing.
Petraeus, a retired four-star Army general who once was seen as a potential presidential candidate, met with President Obama on Thursday and said he intended to step down because of the affair, Obama administration officials said. The president accepted his resignation Friday.
"After being married for over 37 years, I showed extremely poor judgment by engaging in an extramarital affair," Petraeus said in a statement distributed to the CIA workforce Friday. "Such behavior is unacceptable, both as a husband and as the leader of an organization such as ours. This afternoon, the president graciously accepted my resignation."
A senior administration official said the administration learned only on Wednesday that Petraeus had a potentially serious problem. The official said that Petraeus, who turned 60 Wednesday, telephoned Thomas Donilon, the national-security adviser, early Thursday and asked to meet with Obama.
The investigation is not expected to result in any accusations of criminal wrongdoing by Petraeus or Broadwell, according to the two law-enforcement officials, who spoke on condition of anonymity.
Paul Bresson, an FBI spokesman, refused to comment. Attempts to reach Broadwell were unsuccessful. A CIA spokesman declined to answer questions about the timing of the affair or Petraeus' decision to disclose the information.
Current and former U.S. military officials said suspicions of infidelities had followed Petraeus for several years.
The sudden departure of Petraeus created turmoil in the administration's national-security team just days after the president's re-election. That team was expected to see a series of changes in the coming months, but many believed Petraeus would remain in his position.
Obama said Petraeus has "provided extraordinary service to the United States for decades," adding that "through his lifetime of service David Petraeus has made our country safer and stronger."
The statement did not directly address Petraeus' reason for resigning, but the president said his "thoughts and prayers are with Dave and Holly Petraeus, who has done so much to help military families through her own work. I wish them the very best at this difficult time."
Holly Petraeus is an assistant director of the U.S. Consumer Financial Protection Bureau, where she is charged with advocating on behalf of service members and their families. She and her husband met in 1973 at the U.S. Military Academy at West Point, where her father was superintendent. They have a son and a daughter; their son led an infantry platoon in Afghanistan.
"A more personal side"
Broadwell, who also is married, is a West Point graduate and a research associate at Harvard University.
She is the co-author of "All In: The Education of General David Petraeus." The book's co-author was Vernon Loeb, local editor at The Washington Post.
In earlier interviews, Broadwell described meeting Petraeus in 2006 at Harvard, where she was working on a dissertation about leadership. She said they soon started emailing and discussing her research.
In the preface to the book, Broadwell said that after Obama picked Petraeus to lead U.S. forces in Afghanistan in June 2010, the general invited her to Kabul and she decided to turn her dissertation into a biography. She made repeated trips to Afghanistan to spend time observing Petraeus.
In describing Petraeus in a CBS News interview two months ago, she said: "He, at the end of the day, is human and is challenged by the burdens of command. ... So, he has this mask of command — you think he's really confident — but I got to see a more personal side. He's confident, but he's also very compassionate about the loss of troops and sacrifices we're making in Afghanistan."
Deputy steps up
Michael Morell, who served as Petraeus' deputy at the CIA, will serve as interim director. Morell is seen as a leading candidate to replace Petraeus, but there are others, including Michael Vickers, a former CIA paramilitary officer now serving as undersecretary of defense for intelligence.
Petraeus was scheduled to testify next week on Capitol Hill in hearings about the Sept. 11 deaths of four Americans, including the U.S. ambassador and two CIA security officers, in Benghazi, Libya.
U.S. officials insisted the controversy surrounding the attack — and the administration's shifting accounts of it — played no role in Petraeus' decision to resign.
Morell rather than Petraeus now is expected to testify at the closed congressional briefings next week.
Petraeus's 14-month tenure as CIA director is one of the shortest in agency history.
A fitness buff and avid runner who earned his doctorate in international relations from Princeton University, Petraeus came into the CIA job after a highly decorated Army career. His command of the war efforts in Iraq and Afghanistan made him one of the most venerated officers of his generation.
Storied military career
The nature of his resignation is likely to leave a stain on the polished reputation he cultivated during his 37-year military career. He was widely credited with helping to reverse the course of the war in Iraq and overhauling the military's approach to counterinsurgency fighting.
Petraeus was later handed command of the war in Afghanistan, where success proved more elusive.
Because of his evident ambition and abundant publicity, some military rivals saw Petraeus as preening and self-aggrandizing. He did little to discourage speculation that he could be a presidential or vice-presidential candidate and quietly campaigned for the CIA job when his path to higher military positions was blocked.
At the agency, Petraeus presided over an expansion of the CIA's Predator drone campaign in Yemen and was recently behind a push to expand the agency's drone fleet. He was involved in decisions to carry out controversial strikes, including the Predator attacks last year that killed two U.S. citizens: the al-Qaida figure Anwar al-Awlaki and his teenage son.
Petraeus, who retired from the military last year, is still subject to the Uniform Code of Military Justice, which classifies adultery as a crime.
Practically speaking, however, the odds are extremely low that the military would prosecute a retired officer for having an affair, said Eugene Fidell, a prominent military-law expert who teaches at Yale University.
In public appearances, Petraeus has frequently praised his wife for her sacrifices and contributions to his career, and he characterized his return to Washington as an opportunity for them to be closer after his years-long assignments overseas.
Material from The Associated Press snd McClatchy Newspapers is included in this report.
Paula Broadwell co-authored biography.