We have our first major resignation of the second term Obama Administration. It happens to be very unexpected – because of the individual and the reason.

NBC reported Friday that CIA director David Petraeus has resigned from the CIA, citing an extramarital affair.

NBC’s Andrea Mitchell said the resignation was submitted in a letter dated Friday and was accepted by the White House.

In a letter, Petraeus noted that he had been married for 37 years and had exercised “extremely poor judgment’ in conducting an extramarital affair.

Petraeus has only been CIA Director for a little over a year. The President put him in charge of the surge in Afghanistan after firing Gen. Stanley McChrystal in 2010. A year later, Petraeus and Leon Panetta did a kind of swap, with Panetta moving from running the CIA to the Secretary of Defense, while Petraeus moved into the CIA Director’s chair.

The CIA has become much more of a military organization rather than an intelligence collection organization over the first Obama term. It has beefed up its covert presence and runs one of the major Predator drone programs. Petraeus recently sought an expansion of the CIA drone fleet. This is part of the new American way of war, away from the prying eyes of the public or even the proper oversight areas in Congress.

It’s a bit odd to see Petraeus resign just over an extramarital affair; speculation will certainly focus on the possibility that the partner was someone inside the agency, which raises all sorts of ethical issues. And needless to say, this tarnishes the star of Petraeus inside the Beltway, where he was seen as someone who could do no wrong. (I’m not sure why this tarnishes it and not, say, the killing of American citizens without due process, but that’s the way these things work in Washington.)

This was not someone that the White House expected to have to replace, and will make the second term cabinet selection even more arduous.

…I also feel bad for Holly Petraeus, who by all accounts has done good work at the Consumer Financial Protection Bureau focused on consumer fraud against military families.