WASHINFGTON, (AP) — Biographer Paula Broadwell, with whom former CIA Director David Petraeus is said to have had an affair, is a reserve US Army officer.

In the preface to her book - All In: The Education of General David Petraeus — she 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.

She graduated from West Point with academic, fitness, and leadership honours, according to a biography posted on her publisher's website that lists authors available for speaking engagements.

The biography said she had "lived, worked, or travelled in more than 60 countries during more than 15 years of military service and work in geopolitical analysis and counterterrorism and counterinsurgency operations". It said she had spent time with the US intelligence community, US Special Operations Command and FBI Joint Terrorism Task Forces.

Harvard invited some students to meet with Petraeus, and Broadwell was among them because of her military background, which she wrote included being recalled to active duty three times to work on counterterrorism issues after the September 11 attacks.

"I had since joined the Army Reserve and begun graduate studies with the intent of returning either to active duty or to the policy world," she wrote in the preface. She introduced herself and described her research interests. He gave her his card and offered to connect her with others working on the same issues.

"I later discovered that he was famous for this type of mentoring and networking, especially with aspiring soldier-scholars. He immediately responded to the email, inviting me to bounce ideas off him. I took full advantage of his open-door policy to seek insight and share perspectives," Broadwell wrote.

In 2008, she wrote, she was pursuing a PhD in public policy and embarking on a case study of Petraeus' leadership. At one point, she said, he invited her for a run along the Potomac River with his team while he was in Washington.

"I'd earned varsity letters in cross-country and indoor and outdoor track and finished at the top of my class for athletics at West Point; I wanted to see if he could keep stride during an interview. Instead, it became a test for me." He eventually increased the pace "until the talk turned to heavy breathing and we reached a six-minute-per-mile pace. It was a signature Petraeus move. I think I passed the test, but I didn't bother to transcribe the interview."

After Obama put Petraeus in charge in Afghanistan in 2010, Broadwell decided to expand her research into an authorised biography.

She 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, and was 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.