Earlier today, news broke that David Petraeus was resigning because an affair he'd had with Paula Broadwell, the co-author of his biography, All In: The Education of General David Petraeus, a book title about which there are no easy jokes. According to the Wall Street Journal, it was an FBI investigation into the use of Petraeus's Gmail that brought the affair to public knowledge.

The computer-security investigation-which raised questions about a potential compromise to national security-points to one reason Mr. Petraeus and the White House decided he couldn't remain in the senior intelligence position. An extramarital affair has significant implications for an official in a highly sensitive post, because it can open an official to blackmail. Security officials are sensitive to misuse of personal email accounts-not only official accounts-because there have been multiple instances of foreign hackers targeting personal emails.

NBC News reports that the FBI is now investigating Broadwell for "for improperly trying to access his email and possibly gaining access to classified information," although their source notes charges are unlikely.

As for the affair, the WSJ reports it began sometime in August 2011 after Petraeus retired from the Army and ended several months ago.

Broadwell's website is no longer up, but before it was taken down the New York Observer grabbed most of the relevant information. Among other things, the site noted she's married to Scott Broadwell ("They love to run, ski, and surf together") with whom she has two children, that she is "a research associate at Harvard University's Center for Public Leadership and a PhD candidate in the Department of War Studies at King's College London" and that the biography grew out of her dissertation, which she described as a "a study in transformational leadership and organizational innovation influenced by U.S. Army General David Petraeus."

The Observer also dug up part of a reading Broadwell gave at a DC bookstore in February in which she explained how she met Petraeus.

"He came to Harvard University where I was a graduate student and wanted to speak with students about the merits of [the] counter-insurgency approach to fighting the Iraq War, which we were losing at the time….I went up to him and said I'm writing my thesis on negotiating with terrorists and I think it could help your team win and you should really read it and he was kind of enough to indulge me and take the paper and give me his business card. We kept in touch via email for a couple years, and I was still a graduate student. Two years later, I reached out to him if he would speak to students at Havard…He agreed to do a video teleconference from Baghdad. I asked him if I could use him as a case study in my doctoral dissertation, and he agreed."

Also of note: Broadwell published a post in Newsweek early Monday morning called "General David Petraeus's Rules for Living," the timing of which makes it seem like the shit hit the fan relatively recently.

Petraeus's fifth rule for living?

We all will make mistakes. The key is to recognize them and admit them, to learn from them, and to take off the rear­ view mirrors-drive on and avoid making them again.

Duly noted.