2003

March 20

U.S. and British troops invade Iraq after an air attack on Baghdad.

May

Coalition Provisional Authority starts running U.S. occupation and orders Iraqi army dissolved. In front of a “Mission Accomplished” banner, President George W. Bush says major fighting in Iraq has ended.

Aug. 19

One of the first major insurgent bombings targets the U.N. building in Baghdad.

Dec. 13

Saddam Hussein captured.

2004

April

Photos published of U.S. soldiers abusing Iraqi prisoners at Abu Ghraib.

U.S. troops attack Sunni insurgents in Fallujah.

April-May

U.S. troops fight Shiite militias in Karbala, Najaf and Baghdad’s Sadr City.

June 28

Iraqi interim government, named by U.S., officially takes over from the CPA.

July 1

Gen. George W. Casey Jr. replaces Lt. Gen. Ricardo Sanchez as the top U.S. commander in Iraq.

Aug. 15-18

Conference of Iraqi leaders selects a national assembly to advise interim government.

2005

Jan. 30

Elections for a transitional government.

May

Marines begin large-scale operations against insurgents near Syrian border.

September

Fighting in Anbar province, Tall Afar intensifies.

Oct. 15

Constitution approved in referendum.

Dec. 15

Elections for a permanent government.

2006

Feb. 22

Shiite shrine in Samarra bombed, sparking sectarian fighting.

April-May

Shiite Nouri al-Maliki is named prime minister and forms a unity government with Sunnis and Kurds.

June 8

The leader of al-Qaeda in Iraq is killed in an airstrike.

November

Pentagon calls the Shiite Mahdi Army militia the greatest threat to security in Iraq.

Nov. 8

Defense Secretary Donald H. Rumsfeld resigns. Bush later nominates Robert M. Gates to replace him.

Dec. 30

Saddam Hussein is hanged at an Iraqi army base in Baghdad after being found guilty of crimes against humanity.

2007

Jan. 10

Bush announces a new combat troop buildup, known as the “surge.”

Feb. 10

Command of U.S. forces transferred from Gen. Casey to Gen. David H. Petraeus.

June

Insurgent violence is diminished by the “Awakening,” a movement of Sunni tribal members working with U.S. forces.

Sept. 16

Blackwater private security guards open fire in a Baghdad square, killing 17 Iraqis.

2008

Jan. 12

Iraqi parliament passes legislation to let some former members of Hussein’s Baath Party return government jobs.

Feb. 13

Iraqi parliament passes an amnesty law to release Sunni prisoners being held in Iraqi custody.

March

Prime Minister Maliki launches an offensive against Shiite militias, including Moqtada al-Sadr's Mahdi Army.

Sept. 16

Gen. Petraeus takes charge of the U.S. Central Command, and Gen. Ray Odierno assumes command in Iraq.

Nov. 27

A security pact calling for the withdrawal of all U.S. troops from Iraq by the end of 2011 is approved.

2009

January

Iraq’s military takes control of operations.

President Obama is inaugurated.

Jan. 31

Provinces hold council elections (except in Kirkuk and the provinces overseen by the Kurdistan Regional Government).

Feb. 27

Obama says combat troops will be withdrawn by August 2010.

June 30

U.S. troops leave urban areas.

2010

March 7

Parliamentary elections held. No coalition wins a majority of seats.

August

Last U.S. combat brigades are pulled out of Iraq, leaving a training force of approximately 50,000.

Sept. 1

Operation Iraqi Freedom ends and Operation New Dawn begins. Lt. Gen. Lloyd J. Austin III will become top U.S. commander in Iraq.

2011

Dec. 31

All U.S. military forces scheduled to leave Iraq.