WASHINGTON -- Shortly before David Petraeus took charge at the CIA in September 2011, he stood on a sunny parade ground in his Army dress uniform, his wife at his side, and enjoyed a military retirement ceremony unlike any in recent memory.
A band played patriotic marches, a formation of soldiers crisply saluted, and the nation's top commanders praised him as the greatest officer of his generation for averting a U.S. defeat in Iraq and rescuing the war in Afghanistan.
"You now stand among the giants not just in our time but of all time, joining the likes of Grant and Pershing and Marshall and Eisenhower as one of the great battle captains of American history," proclaimed Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, as hundreds cheered and Petraeus beamed.
Now, a little more than 14 months later, Petraeus' boundless career and sterling reputation are in tatters following his resignation as spy chief after admitting adultery with his biographer.
What happened to the squeaky-clean leader who seemed to embody all that the Army and the nation glorify -- heroism, honor and victory? The answer, former aides and officers who served under him say, is that Petraeus, 60, had changed from the vigilant officer who had rocketed up the ranks. Once at the top, he had grown accustomed to the adulation. He grew fixated with his carefully burnished image, and grew more isolated from those who might counsel caution.
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After moving to the CIA, he decorated his office with military medals and souvenirs from his combat tours, but had to adjust to life out of the limelight. He lived in a quiet bedroom suburb of Washington after years in war zones during which he saw his wife mostly on brief leaves or when he was called back to testify before Congress. He arrived at the CIA without the aides who had served him for years. In their place were spies and civilians who prize independence, not military deference.
"He was taken out of his comfort zone," said Steve Boylan, a retired Army colonel and longtime Petraeus aide. "He spent 37 years in uniform, and all of a sudden the routine you had is gone, the people you relied on as close advisers are gone. I think he was feeling a little vulnerable."
'He was her mentor'
Others saw a simpler explanation for his extramarital affair with Paula Broadwell, a West Point graduate and Army Reserve officer. They first met in 2006 when she approached him after he spoke at Harvard, and he gave her his card. By her account, she ultimately spent hundreds of hours with him. She was gathering material for a fawning biography that was published in January.
"I don't underestimate the power of human beings to be attracted to each other when they have a lot in common," said a former senior CIA official who counts Petraeus as a friend. "He was her mentor; she was his admirer. The only thing extraordinary here is that he is so famous."
Petraeus had met his wife, Holly, on a blind date while he was a cadet at West Point and she was home from college. Her father, an Army general, was superintendent of the military academy. They married in 1974 in the West Point chapel.
Like any young Army couple, they moved almost yearly over the next three decades -- sometimes to exotic overseas posts like Vicenza, Italy, where Petraeus served in an airborne unit in the mid-1970s, and to less cosmopolitan areas, like Fort Campbell, in rural Tennessee.
From the start, every competition, every assignment was a chance to excel. As a junior company commander at Fort Stewart, in southeastern Georgia, he drilled his men for weeks to win an "Expert Infantry Badge" unit citation, an award few other lieutenants even realized existed. But winning the award "put Petraeus on the map," his battalion commander later said.
Holly Petraeus told interviewers that she sometimes longed for her husband to spend more time with her and their two children. When he took a leave in 1984 to get a master's degree at Princeton University, she said she hoped it would be a respite from their busy life. But Petraeus decided to get a doctorate instead, cramming all the course work into two years.
After Petraeus led the 101st Airborne Division in the 2003 invasion of Iraq, the family spent much of the next decade apart. By the time he took over the war in Afghanistan in 2010, he was more cautious, more concerned about his image, and most importantly, more alone.
The brainy general had surrounded himself with a brilliant staff in Iraq. In Afghanistan, he had few close aides. Many of his longtime staff had moved on to more senior jobs.
"He had changed a lot when he arrived in Afghanistan -- very self-isolated," said a U.S. official who worked with him for much of the decade. "Unless he had a work dinner, he always ate by himself. Few were let in to his very, very small circle."
Broadwell, who is married and 20 years younger than Petraeus, managed to join the core group, according to several officers and aides. During multiple trips to Afghanistan, she stayed at Petraeus' headquarters in Kabul and occasionally accompanied the four-star general on helicopter trips to visit combat units in the field.
When Petraeus was preparing to hand over command to Marine Gen. John Allen last summer, one newly arrived officer was surprised to see Broadwell in meetings at the Kabul headquarters.
"I was a little surprised at how much unescorted time she got with him," the officer said, "but it was explained to me that that was how Petraeus wanted it."