WASHINGTON – David Petraeus, the retired four-star general who led the U.S. military campaigns in Iraq and Afghanistan, has resigned as director of the CIA after admitting he had an extramarital affair.

The resignation shocked Washington's intelligence and political communities, representing a sudden end to the public career of the best-known general of the post 9/11 wars.

According to a statement he sent to CIA employees, Petraeus asked President Barack Obama on Thursday to allow him to resign and on Friday the president accepted. Petraeus said he had shown "extremely poor judgment" in having the affair.