—March 20: U.S. forces attack Baghdad with missiles and bombs in a failed attempt to kill Saddam Hussein. U.S. and allied ground troops roll into Iraq.
—April 9: American troops storm Baghdad and the statue of Saddam is toppled in Firdous Square, the symbolic collapse of his regime.
—May 1: President George W. Bush declares an end to major combat operations.
—July 22: Saddam's sons Oday and Qusay are killed in a gunfight in Mosul.
—Aug. 7: A car bomb strikes the Jordanian Embassy, the first such attack of the war. Twelve days later, a truck bomb demolishes the headquarters of the United Nations in Baghdad, killing top U.N. envoy Sergio Vieira de Mello and 21 others.
—Sept 3: U.S. announces an Iraqi administration largely made up of Iraqi exiles who opposed Saddam.
—Oct. 26: A barrage of rockets slams into the Al-Rasheed Hotel in the Green Zone, killing an American lieutenant colonel and injuring 17 other people. Deputy Defense Secretary Paul Wolfowitz, one of the architects of the war, who was visiting Baghdad, escapes injury.
—Dec. 13: Saddam is captured in an underground hideout near Tikrit.
—Feb. 1: Two suicide bombers attack Kurdish political offices in Irbil, killing 117 people and injuring 133.
—March 2: Multiple explosions rock Baghdad and Karbala at the climax of a Shiite festival, killing nearly 200 people in the deadliest attack so far.
—March 31: Four Blackwater security contractors are ambushed and killed in Fallujah, setting off the first battle for the insurgent-dominated city west of Baghdad.
—April 4: Followers of Shiite cleric Muqtada al-Sadr launch attacks across southern Iraq after the U.S tries to close his newspaper. Fighting rages until the end of August.
—April 18: U.S. announces an investigation into abuses against detainees at the Abu Ghraib prison as gruesome photos emerge showing Iraqi prisoners humiliated.
—May 17: The head of the Iraqi Governing Council, Ezzedine Salim, is killed in suicide attack near the entrance to the Green Zone.
—May 19: U.S. jets mistakenly bomb a wedding party in western Iraq, killing 42 people, including women and children.
—June 28: The U.S. transfers sovereignty to the Iraqis but retains most real power. The civilian head of the occupation authority, L. Paul Bremer, leaves the country.
—July 1: Trial of Saddam begins with the ousted leader appearing at his first hearing.
—Sept. 30: A car bomb strikes American troops handing out candy to children, killing up to 35 children.
—Nov. 7: U.S. soldiers and Marines launch the biggest attack of the war to date to seize the insurgent stronghold of Fallujah.
—Dec. 21: A bomb kills 22 people, including 18 Americans, at Forward Operating Base Marez in Mosul.
—Jan. 26: A helicopter crashes in western Iraq, killing 31 Americans.
—Jan. 30: Iraqis select a new parliament in the first elections since the fall of Saddam. Shiite and Kurdish parties take an overwhelming majority after Sunnis largely boycott.
—Feb. 28: A vehicle bomb kills 127 people in Hillah in the deadliest blast to date.
—March 4: Italian journalist Giuliana Sgrena is freed by Italian intelligence but the rescuing agent is killed when U.S. troops fire on their vehicle en route to Baghdad airport.
—Aug. 28: An Iraqi commission submits a draft constitution to parliament.
—Aug. 31: Rumors of a suicide bomber panics Shiite marchers in a religious procession at a Baghdad bridge and nearly 10,000 people reportedly die in the stampede.
—Sept. 14: A series of bombings kills 160 people in Baghdad in a dramatic escalation of the insurgency.
—Oct. 15: Iraqis approve the new constitution in a referendum.
—Oct. 24: The Palestine and Sheraton hotels, favored by Western journalists, are struck by multiple truck bombs.
—Nov. 19: U.S. troops kill 24 people, including 15 noncombatants, in Haditha after an insurgent attack.
—Dec. 15: Iraqis choose a new parliament in the first election under the new constitution.
—Feb. 22: Sunni militants bomb the Shiite Golden Dome shrine in Samarra, triggering a wave of sectarian violence that brings Iraq to the brink of civil war.
—June 7: The leader of al-Qaeda in Iraq, Abu Musab al-Zarqawi, is killed in a U.S. airstrike northeast of Baghdad.
—June 17: U.S. troops launch a battle to take control of the western city of Ramadi in a bloody conflict that persists for more than a year.
—July 9: Shiite militias kill 40 Sunnis in the Jihad neighborhood of Baghdad as sectarian war spreads to the capital.
—Nov. 23: Bombs kill more than 200 Shiites in Baghdad's Sadr City neighborhood.
—Dec. 30: Saddam is executed by hanging.
—Jan. 10: President Bush orders 30,000 reinforcements to Iraq in an effort to stem the sectarian war and stabilize Baghdad.
—Jan. 28: Followers of a Shiite cult launch a battle in Najaf that kills nearly 300 people.
—Feb. 3: A bomb in a Baghdad market kills 135 people.
—Feb. 27: Shiite militias besiege British bases in Basra, ultimately prompting most British forces to leave the country.
—March 23: Iranians seize 15 British navy personnel patrolling near Basra, releasing them April 4.
—March 27: A blast in Tal Afar kills 152 people, setting off a wave of Shiite reprisals that claim 70 Sunni lives.
—April 18: Bombs across Baghdad kill nearly 200 people.
—Aug. 14: A series of bombings directed against the Yazidi religious community in the north kills nearly 800 people.
—Aug. 29: Muqtada al-Sadr announces a cease-fire after a public backlash against his militia following a clash in Karbala that killed 50 people. Attacks against U.S. troops in Shiite areas begin to drop.
—Sept. 16: Blackwater security guards mistakenly believing they were under attack kill 17 civilians in Nisoor Square in Baghdad.
—Jan. 8: U.S. and Iraqi forces launch operations in Baghdad to secure the capital.
—Jan. 23: Operations begin in Mosul against al-Qaida's last major urban stronghold.
—Feb. 21: Turkey launches an offensive in northern Iraq against Kurdish rebels from the PKK.
—March 25: Heavy fighting breaks out in Basra as Iraqi forces try to crush Shiite militias, which launch counterattacks in Baghdad. Fighting rages for a month until the Shiites accept a cease-fire.
—Oct. 26: U.S. special operations troops strike in Syria to break up a ring smuggling weapons and fighters into Iraq.
—Nov. 27: The Iraqi parliament approves an agreement with the U.S. calling for the departure of all U.S. troops by the end of 2011.
—May 27: The last British combat troops leave Iraq.
—Aug. 19: A massive truck bomb kills about 100 people in Baghdad.
—Oct. 25: Bombs targeting government buildings kill 127 in Baghdad.
—March 7: Iraqi parliamentary election fails to give power to a single bloc, leading to months of political negotiations and infighting that drag on until a power-sharing deal in November.
—Aug. 18: U.S. combat operations in Iraq end as its last combat brigade departs for Kuwait. Thousands of troops remain behind in a supporting role.
—April 8: The Iraqi army raids Camp Ashraf, home to Iranian exiles. The raid kills 34 civilians and produces calls for the Iraqi government to honor agreements for the protection of the camp.
—May 5: Car bomb in Hillah kills nearly 30 people.
—June 21: A bomb in the southern city of Diwaniyah kills 20 and injures 30.
—Oct. 21: President Barack Obama announces all troops will leave Iraq by the end of the year.
—Dec. 15: The U.S. military officially declares the end of its mission.