(CNN) -- The last U.S. troops in Iraq crossed the border into Kuwait on Sunday, marking the end of an almost-nine year war. According to the defense department, 4,487 service members were killed in the war; more than 30,000 were wounded. In all, 1.5 million Americans served their nation at war. It is impossible to know with certainty the number of Iraqis who have died in Iraq since 2003.
Here are some key dates in the conflict:
March 20: President George W. Bush appears on television screens across America and in a four-minute speech says, "My fellow Americans, at this hour, American and coalition forces are in the early stages of military operations to disarm Iraq, to free its people and to defend the world from grave danger."
April 9: U.S. forces topple a statue of Saddam Hussein in Baghdad's Firdos Square, marking the symbolic fall of his regime.
May 1: Standing under a banner that read "Mission Accomplished" aboard the aircraft carrier USS Abraham Lincoln, Bush declares that major combat operations in Iraq is over. The pronouncement later turns out to be premature.
October 2: The head of the CIA's search for banned weapons in Iraq says his group has found no weapons of mass destruction, the reason the Bush administration had cited for going to war.
December 13: Coalition forces capture Saddam Hussein at the bottom of a ventilated "spider hole" six to eight feet underground in Adwar, near a compound of ramshackle buildings about 9 miles (14 kilometers) outside his hometown of Tikrit. He offers no resistance.
April 28: Photographs from Abu Ghraib prison spark international outrage after they show detainees in degrading positions, with American soldiers posing next to them and smiling. The images show naked prisoners stacked on top of each other, or being threatened by dogs, or hooded and wired up as if for electrocution.
January 30: Defying insurgent attacks, Iraqi voters cast ballots in a milestone election designed to steer the country down the road of democracy. It is the first free election in half a century.
June 7: A U.S. air strike kills Abu Musab al-Zarqawi, the leader of the terrorist group al Qaeda in Iraq.
December 30: Saddam Hussein is hanged. He was 69.
January: Bush deploys 30,000 additional troops, a "surge" strategy designed to quell violence and restore security.
November 27: The Iraqi parliament ratifies a security agreement with the United States that says U.S. combat forces will be completely out of Iraq by December 31, 2011.
February 27: President Barack Obama approves a plan to withdraw roughly two-thirds of all U.S. troops from Iraq by the end of August 2010, with the remaining out of the country by the end of the following year.
January: With the departure of British, Australian and Romanian troops from Iraq, Multi-National Forces-Iraq undergoes a name change to United States Forces-Iraq
August: No U.S. troops were killed in Iraq in August, marking the first month without an American military death there since the United States invaded the country.
December 15: The U.S. mission formally ends with a flag casing ceremony in Baghdad.
December 18: In a final tactical road march, the last U.S. troops in Iraq cross the border into Kuwait.