One of the major blunders the United States made, the experts said, was falling into "mission creep" -- the expansion of a mission beyond its original objectives.

    While U.S. troops succeeded in the missions they were given, military planners did not have any clear-cut goals.

    While Washington initially aimed to unseat former Iraqi President Saddam Hussein, the mission changed from finding weapons of mass destruction to supporting a democracy, then to stopping the insurgency.

    Such a scenario was what military thinkers such as Colin Power, author of the Powell Doctrine -- which holds that a force should go into war only with overwhelming force and a clearly defined objective -- sought to avoid.

    "That should be the lesson for policy makers: do we have a clear mission, or are we just fumbling along?" said Kyle Spector, policy advisor for national security at Third Way.

    The Iraq war will likely influence the decisions of future military planners: if faced with possibility of military action, they will think back to Iraq, he said.

    U.S. experts say the war also demonstrated the U.S. military's effectiveness in conventional operations, as seen in the "shock and awe" campaign, when U.S. forces steamrolled into Baghdad and overthrew Saddam's government in a matter of weeks.

    But despite the initial success, an insurgency arose even as former Defense Secretary Donald Rumsfeld denied its existence.

    Critics said the lack of planning for the after effects of the invasion was one of the worst strategic blunders the United States has ever made.

    Christopher A. Preble, director of foreign policy studies at the Cato Institute, said there were plenty of warning signs that all would not go smoothly after the invasion.

    "I'm a little frustrated by people saying we had no idea this would happen," he said. "Academics and scholars of nation building and post conflict reconstruction understood very well that the analogies to Japan and Germany after World War II were completely flawed."

    Still, it had been many years since the United States had embarked a mission of this scale --full-on regime change -- and the Bush administration did not anticipate having to stay for that long.

    "If a future president is serious about overthrowing a foreign government and replacing it with a government that we like better, it is going to be a long and costly enterprise," he said.

    The war and its strategic failures have given way to an "Iraq syndrome" -- a reluctance to engage in regime change operations and post conflict stabilization and reconstruction, some analysts argued.

    Americans want to move on, a sentiment mirrored in Obama' s speech on Tuesday when he jumped from the subject of Iraq to the U.S. economy, some analysts contended.

    Michael E. O'Hanlon, senior fellow at the Brookings Institution, said the United States will in the future be less inclined to become involved in such conflicts.

    Still, there may be future instances in which Washington is faced with making a decision on whether to use military force and may have few other choices but to go to war, he said.

    But the most important lesson of Iraq is that planning for the after-effects of an invasion is necessary, he said.

    "You can never assume that somehow order will spring up naturally out of chaos," he said.