After Obama put Petraeus in charge in Afghanistan in 2010, Broadwell decided to expand her research into an authorized biography.
Broadwell has deep ties and friendships throughout the Washington media sphere and often was sought for comment on Petraeus' viewpoints as he proved harder and harder to reach.
The CIA director had lowered his media profile, stopping his practice of emailing reporters and ending once-common background interviews by the agency. That was especially the case after GOP allegations last spring that the Obama administration was leaking sensitive material to burnish its foreign policy reputation ahead of the presidential election, after a series of stories appeared about top secret operations aimed at al-Qaida in Yemen, and Iran's nuclear program. A White House-ordered investigation of those leaks continues.
Petreaus's resignation comes just before a crucial scheduled appearance before congressional intelligence committees next week to testify on what the CIA knew, and what it told the White House, before, during and after the attacks that killed the U.S. ambassador and three other Americans in Libya on Sept. 11.
Congressional officials say Petraeus' deputy, Michael Morell, will testify instead, as acting director of the CIA.