In the preface to "All In: The Education of General David Petraeus," published by Penguin in January, Broadwell said she first met Petraeus in the spring of 2006. She was a graduate student at the Kennedy School of Government at Harvard, and he was visiting the university to discuss his experiences in Iraq and a new counterinsurgency manual he was working on.
In 2008, she wrote, she was pursuing a Ph.D. in public policy and embarking on a case study of Petraeus' leadership. After Obama put Petraeus in charge in Afghanistan in 2010, Broadwell decided to expand her research into an authorized biography.
Broadwell made many trips to Afghanistan, with unprecedented access to Petraeus, and also spent time with his commanders across the country. When Petraeus took the job at the CIA, she remained in close contact with him, sometimes invited to his office for events like his meeting with Hollywood actress Angelina Jolie.
With the book done, she told friends she had been concentrating on turning part of her research on Petraeus into a dissertation, to complete her doctorate.
Petraeus, in his email, told his CIA employees that he treasured his work with them "and I will always regret the circumstances that brought that work with you to an end."
Other CIA directors have resigned under unflattering circumstances. CIA Director Jim Woolsey left over the discovery of a KGB mole, and John Deutch left after the revelation that he had kept classified information on his home computer.
Before Obama brought Petraeus to the CIA, Petraeus was credited with salvaging the U.S. war in Iraq.
President George W. Bush sent Petraeus to Iraq in February 2007, at the peak of sectarian violence, to turn things around as head of U.S. forces. He oversaw an influx of 30,000 U.S. troops and moved troops out of big bases so they could work more closely with Iraqi forces scattered throughout Baghdad.
Petraeus' success was credited with paving the way for the eventual U.S. withdrawal.
After Iraq, Bush made Petraeus commander of U.S. Central Command, overseeing all U.S. military operations in the greater Middle East, including Afghanistan and Pakistan.
When the top U.S. commander in Afghanistan, Gen. Stanley McChrystal, was relieved of duty in June 2010 for comments in a magazine story, Obama asked Petraeus to take over in Kabul and the general quickly agreed.
In the months that followed, Petraeus helped lead the push to add more U.S. troops to that war and dramatically boost the effort to train Afghan soldiers and police.
Morell had served as deputy director since May 2010, after holding a number of top roles, including director for the agency's analytical arm, which helps feed intelligence into the president's daily brief. He also worked as an aide to former CIA Director George Tenet.