General Odierno will leave the country Wednesday, after formally turning over command to Lt. Gen. Lloyd J. Austin III. For General Odierno, the ceremony will mark the end of more than four years in Iraq, where he has gone from a commander criticized for heavy-handed operations in regions that became insurgent strongholds to a figure praised, in military circles and beyond, for overseeing the American military buildup here in 2007.

But part of his legacy may rest on the performance of Iraq’s security forces in taking sole control of the country. American officials have conceded they were dealt a blow last week by a wave of car bombings, roadside mines and hit-and-run attacks that insurgents unleashed in at least 13 towns and cities across Iraq.

The attacks were “not unexpected,” General Odierno said. “What I would tell you surprised me a little bit was that they were able to do it over the country with some coordination.”

In his four years here, General Odierno was often at the center of shifting American military strategy in Iraq. He said the military learned lessons “the hard way.”

“We all came in very naïve about Iraq,” he said.

“We came in naïve about what the problems were in Iraq; I don’t think we understood what I call the societal devastation that occurred,” he said, citing the Iran-Iraq war, the Persian Gulf war and the international sanctions from 1990 to 2003 that wiped out the middle class. “And then we attacked to overthrow the government,” he said.

The same went for the country’s ethnic and sectarian divisions, he said: “We just didn’t understand it.”

To advocates of the counterinsurgency strategy that General Odierno has, in part, come to symbolize, the learning curve might highlight the military’s adaptiveness. Critics of a conflict that killed an estimated 100,000 Iraqis, perhaps far more, and more than 4,400 American soldiers might see the acknowledgment as evidence of the war’s folly.