U.S. Army Gen. David Petraeus recognized that the troop surge in Iraq was a risk, and that when he arrived in Iraq 18 months ago, he was "still afflicted by some doubt" about whether it was the right strategy to turn around the war.
"I think you're always doing that in any endeavor that you do," Petraeus told ABC News' Terry McCarthy. "There are no sure things in life."
Success of the Surge
When Petraeus initiated the surge 18 months ago, many believed that his strategy would fail. Overall, violence has plunged in Iraq, and the last of the combat brigades from the surge returned home this month.
But, with four suicide car bombings, apparently all carried out by women in Baghdad and in the northern city of Kirkuk on Monday, Petraeus acknowledged the "very difficult and very diabolical and murderous threat" posed by al Qaeda, and, especially, by female bombers.
"There will be further attacks," Petraeus said. "It is very, very difficult in this culture, because only a female can search another female. Again, there are just multiple points through which females can gain access to the column of people."
Last week, Petraeus met with one of his strongest critics in Congress, Sen. Barack Obama, D-Ill., who opposed the surge and supports a 16-month timetable for withdrawal.
Obama told ABC News' Terry Moran in an exclusive "Nightline" interview that in his meeting with Petraeus, the general discussed his "deep concerns" about "a timetable that doesn't take into account what they anticipate might be a change in conditions."
Petraeus declined to comment about his meeting with the presumptive Democratic presidential nominee, beyond saying that in their private talks, Obama conceded that progress had been made in Iraq.
"We felt we had good exchanges, we felt we were able to describe what has taken place over the last 18 months," Petraeus said.
Petraeus said the U.S. military has completely transformed itself because of Iraq.
"What works in Mosul today, may not work in Tikrit today. In fact, it may not work in Mosul tomorrow," he said.
But, "many of the lessons learned here will apply there," Petraeus said. "Although they may have to be modified or refined for the specific location in Afghanistan."
The main lesson Petraeus highlighted from the surge is that "the only way to secure a population is to live with it."
Petraeus said that patrol bases were located throughout the neighborhoods in Baghdad, because "you can't commute to this fight."
He also stressed the importance of promoting "local reconciliation."
"It's not a case where all the Sunnis moved to one location and the Shia moved to another," Petraeus said. "There are still countless mixed neighborhoods and there are countless neighborhoods in which there was certainly sectarian hardening."
One of the key improvements in the military's organizational strategy in Iraq has been the "fusion of intelligence" between different agencies, organizations and special operations forces, Petraeus said.
"This is information that can allow you to take precise action to target an individual, rather than having to target, say, a neighborhood," he said. "And that helps you avoid the kind of sweep operations where you vacuum up 100 citizens in order to find one."
One of the main guidelines that Petraeus tried to follow in Iraq was "to end up with fewer enemies at the end of each day, rather than more, based on your actions."
Violence has gone down. So far, in July, only five American combat deaths have been reported.
"It's important to remember how bad it was, I think, because Iraq has come a very, very long way from that time … it wasn't just the horrific casualties on a daily basis, almost too many for the morgues to keep up with, it was also the damage done to the society, the fear that came to characterize daily life, and then how can you possibly get anything done?"
The military is engaged in a "continuous assessment," Petraeus said, where they weigh many factors, such as troop strain, the financial toll of deployment, and the sacrifices of American families, among others, to determine if troops can be moved from Iraq to Afghanistan.
Petraeus says he is hopeful that if violence continues to decrease, he will be able to recommend more troop withdrawals by the fall.
In September, Petraeus leaves to take over as the commander of Central Command, with overall responsibilities over the Middle East and central Asia, including Iraq and Afghanistan. Lt. Gen. Ray Odierno, who served as Petraeus' deputy, will fill Petraeus's post.