US General John Allen has decided to retire rather than proceed with his nomination as the NATO supreme allied commander.
In January, General Allen was cleared by Pentagon investigators of accusations of professional misconduct over email exchanges with Jill Kelley, a Florida socialite.
He became ensnared in a scandal that forced General David Petraeus to resign as CIA director in November, after the FBI uncovered an affair between General Petraeus and his biographer, Paula Broadwell.
President Barack Obama on Tuesday announced General Allen is leaving the military.
AAP reports General Allen recently returned from his post as the commander of US and NATO troops in Afghanistan.
He told the Washington Post in an interview published on Tuesday that his decision was not related to the episode over his email exchanges with Ms Kelley.
He said he wanted to focus on helping his wife, Kathy, who has autoimmune disorder, a chronic condition.
"Right now, I've just got to get her well," Gneral Allen said. "It's time to take care of my family."