The 2003 US-led invasion of Iraq was meant to topple a dictator who had inflicted reckless wars and economic misery on his fellow Iraqis, and then to usher in a thriving democracy.
Instead, Iraqis faced years of upheaval and chaos.
A devastating insurgency, first by Saddam Hussein loyalists and then by al Qaeda, was followed by a sectarian civil war and later the rise of Islamic State, which occupied a third of the country and slaughtered thousands.
Here is a look at some of the violence, including suicide bombings and beheadings, that has plagued Iraq, a major OPEC oil producer and key US ally, since the 2003 war.
* March 20, 2003 - US-led forces invade Iraq from Kuwait to oust Saddam Hussein. The attack crushes the Iraqi military and chases Saddam from power in a span of weeks.
* April 9, 2003 - US troops seize Baghdad. Saddam goes into hiding. Lawlessness emerges in Baghdad and elsewhere.
* May 1, 2003 - President George W Bush declares that “the United States and our allies have prevailed” in Iraq. As he spoke aboard the aircraft carrier Abraham Lincoln, a banner behind him stated, “Mission Accomplished.”
* May 23, 2003 - Coalition Provisional Authority head Paul Bremer disbands Iraq's army and intelligence services, sending hundreds of thousands of angry armed men into the streets.
* Aug 7, 2003 - At least 17 people are killed in a truck bomb attack on Jordan's embassy in Baghdad.
* Aug 19, 2003 - Suicide truck bomb wrecks UN headquarters in Baghdad, killing 22 people including UN envoy Sergio Vieira de Mello.
* Aug 29, 2003 - A car bomb kills at least 83 people, including top Shi’ite Muslim leader Ayatollah Mohammed Baqer al-Hakim, at Imam Ali mosque in Najaf.
* Summer 2003 - Insurgency against US-led forces emerges, waged by pro-Saddam guerrillas, then al Qaeda and Shi'ite fighters. US forces fail to find weapons of mass destruction.
* Dec 13, 2003 - US troops capture Saddam, bearded and bedraggled, hiding in a hole near Tikrit.
* Spring 2004 - Insurgency intensifies in Falluja and elsewhere in mainly Sunni Muslim Anbar province and violence by followers of Shi'ite cleric Moqtada Sadr in the south. US faces international condemnation after photographs emerge showing abuse of detainees at Abu Ghraib jail.
* March 31, 2004 - In Fallujah four Blackwater private security contractors are killed and some of the burnt bodies hung from a bridge.
* May 11, 2004 - Kidnappers behead US businessman Nicholas Berg and videotape his killing.
* October 2004 - Al Qaeda leader in Iraq Abu Musab Al-Zarqawi starts waging bloody attacks designed to turn majority Shi’ite Muslims against minority Sunnis in a civil war.
* June 8, 2006 - Zarqawi is killed by US forces.
* Dec 30, 2006 - Saddam Hussein hanged by masked executioners after Iraqi court sentences him to death for killings of 148 men and boys in northern Iraq in 1982.
* January 2007 - Bush announces a new war strategy including a “surge” of US troops into Iraq to combat the insurgency.
* October 2007 - Iraq says security guards from the US firm Blackwater “deliberately killed” 17 Iraqis in a shooting in Baghdad, and plans legal steps against them. Blackwater says its guards reacted lawfully to an attack on a convoy.
*Aug 2010 - Last US combat brigade leaves Iraq.
* July 4, 2014 - Islamic State leader Abu Bakr al-Baghdadi seizes world's attention by climbing the pulpit of Mosul’s medieval al-Nuri mosque in black clerical garb on a Friday to declare his caliphate.
*2017 - Islamic State's brutal rule, during which it killed and executed thousands in the name of a narrow interpretation of Islam, comes to an end in Mosul when Iraqi and international forces defeat the group there.
* Oct 19, 2018 - President Donald Trump declares ISIS defeated.
* Oct 27, 2019 - Trump announces Islamic State leader Abu Bakr al-Baghdadi killed himself during a night raid by US special forces in Syria. Baghdadi dies alongside three of his children by detonating an explosives-laden vest when he fled into a dead-end tunnel during the attack.