The United States marks the end of the war in Iraq. As U.S. Defense Secretary Leon Panetta attends the final flag ceremony, he did not speak of victory in Iraq and did not declare Mission accomplished. SOUNDBITE (English) U.S. DEFENSE SECRETARY LEON PANETTA, SAYING: "After a great deal of blood has been spilled by both Iraqis and Americans, the mission of an Iraq that could finally govern and secure itself, has become real. " Now, after the U.S.-led invasion of Iraq ousted Saddam Hussein, American troops are pulling out and leaving behind a country still battling insurgents, political uncertainty and sectarian divisions. Nearly 4,500 U.S. soldiers and tens of thousands of Iraqis lost their lives in a war that began with a "Shock and Awe" campaign of missiles and bombs pounding Baghdad, but later descended into a bloody sectarian struggle between long-oppressed majority Shi'ites and their former Sunni masters. Major General Jeffrey Buchanan, told Reuters it is too soon to tell if it was worth it. SOUNDBITE (ENGLISH) MAJOR GENERAL JEFFREY BUCHANAN, SAYING: "I don't think any of us know exactly what is going to happen in the future, and it is hard to make a judgment about how worthwhile it has been until we have the benefit of that knowledge," Saddam is dead and the violence has ebbed. But the U.S. troop withdrawal leaves Iraq with a score of challenges from a stubborn insurgency and fragile politics to an oil-reliant economy plagued by power cuts and corruption. Retired Lieutenant Army Colonel John Nagl, is the President of the Center for a New American Security in Washington, D.C. SOUNDBITE (ENGLISH) JOHN NAGL, PRESIDENT OF THE CENTER FOR AMERICAN SECURITY, SAYING: "The direction Iraq takes next, is largely going to determine whether the effort, the extraordinary effort we put into this, the costs we paid; the costs the Iraqi people paid, end up being anything like a reasonable return on investment -- it doesn't look like it right now." Iraq's neighbors will keep a close watch on how Baghdad will confront its problems without the buffer of a U.S. military presence, while a crisis in neighboring Syria threatens to upset the region's sectarian and ethnic balance. SOUNDBITE (ENGLISH) JOHN NAGL, PRESIDENT OF THE CENTER FOR AMERICAN SECURITY, SAYING: "It is not a satisfying feeling that we have built a country that we can depend upon, we have not created a true ally. Iraq's at least tacit support for the regime in Syria, its links it continued links to an oppressive and abhorrent regime in Iran, all mean that the results are very muddied and unclear. I think the American people are seeing an unsatisfying end to a very unsatisfying very divisive and difficult war." At the height of the war, 170,000 American soldiers occupied more than 500 bases across the country. All will be home before the end of the year when a security pact expires. SOUNDBITE (ENGLISH) JOHN NAGL, PRESIDENT OF THE CENTER FOR AMERICAN SECURITY, SAYING: "There is a very heavy bill that comes with this war." Every day hundreds of trunks and troops trundle in convoys across the Kuwaiti border as U.S. troops end their mission. Deborah Lutterbeck, Reuters.