|In the aftermath of the invasion Iraq became a battleground between coalition forces, local fighters [GALLO/GETTY]
Following the September 11, 2001, attacks, the US invaded Afghanistan with the goal of dismantling the al-Qaeda network and seizing its leader, Osama bin Laden.
Heightened security concerns in the US, and allegations that Iraq possessed weapons of mass destruction, prompted an invasion by US and other Western forces which led to the toppling of Iraqi dictator Saddam Hussein, although no WMD's were ever found.
American troops have been a constant presence across Iraq’s landscape since then. Some 45,000 were still on the ground earlier this year, but under the terms of a security pact, they will fully withdraw by the end of 2011.
Al Jazeera takes a look at the last eight years in the battle for hearts, minds and military might in Iraq:
US President George W Bush warns that the world needs to act against the increasing dangers posed by Saddam Hussein's pariah regime in Iraq.
At the same time, UK Prime Minister Tony Blair publishes a dossier on Iraq’s military capabilities, later seen to be suspect.
A UN resolution threatens serious consequences for Iraq if it breaches the terms of a disarmament accord.
UN weapons inspectors return to Iraq to investigate the validity of claims that the country possesses WMD's.
Hans Blix, the chief weapons inspector for the UN, says inspectors need more time to verify Iraq’s compliance with the UN resolution.
The UK’s ambassador to the UN says the diplomatic process on Iraq has ended as arms inspectors leave the country.
A US-led invasion of the country begins on March 20, 2003 with a force of 150,000 American troops and 23,000 soldiers from other countries.
The capital, Baghdad, falls 20 days later, toppling Saddam’s government.
A power struggle emerges among Iraq's Shia communities with some calling for co-operation, and others for resistance.
In December, Saddam is captured after being found hiding underground at a farm in Tikrit.
Loyalists of Moqtada al-Sadr, the Shia cleric, take on Western coalition forces based in the country. Religious leaders warn top US civilian administrator Paul Bremer against blocking Islamic law.
Hundreds are reported killed in fighting during a US military siege of Falluja.
The US hands sovereignty to an interim government headed by Iyad Allawi, as the debate continues about whether Iraq ever had WMD's.
Photographs are unearthed of US troops abusing and humiliating Iraqi prisoners at Abu Ghraib prison, sparking international outcry and a US senate probe of alleged abuses.
Meanwhile, images of gruesome violence in Iraq become well-known across the world via internet videos, as the US claims that Jordanian-born Abu Musab al-Zarqawi's group of fighters has attracted a growing number of supporters.
In July, Saddam appears in court for the first time, facing charges including war crimes and genocide.
In the aftermath of the US invasion, the Iraqi unemployment rate reaches 70 per cent in August.
The first multi-party elections in 50 years are held amid stringent security measures on January 30.
Jalal Talabani, a Kurdish politician, is sworn in as president.
Masoud Barzani becomes the regional president for semi-autonomous Iraqi Kurdistan.
Voters accept a new constitution with aims to create an Islamic federal democracy. Iraqis vote for a government and parliament.
The Arab League chief visits Iraq to prepare for a reconciliation conference, and the US military begins paying Iraqi contractors in dinars rather than in dollars.
The United Iraqi Alliance - a Shia-led party - wins the 2005 election.
President Talabani tasks new prime minister Nouri al-Maliki with forming a new government as Ibrahim al-Jaafari is forced out.
Abu Musab al-Zarqawi, al-Qaeda's leader in Iraq, is killed in an air strike.
In December, Saddam is executed for crimes against humanity as the Baath party names a new leader.
The number of foreign troops in the country drops to just under 127,000 US soldiers and 20,000 from the other coalition countries.
One of the country's most powerful Shia leaders calls for stronger action against Sunni-led fighters.
President Bush announces a new Iraq strategy, including a surge of over 21,000 more troops to be deployed for security in the country, following an escalation in insurgent activity and sectarian strife.
The Iraqi Accordance Front, the main Sunni political bloc, withdraws from cabinet following a dispute.
Britain hands over security of Basra to Iraqi forces, as the country pushes towards reducing the number of its troops in Iraq.
Parliament passes a law allowing former officials of Saddam’s government to return to public life.
Violence continues to escalate despite a troop surge and US support for the Awakening Council.
In April the British defence secretary says the final withdrawal of troops has been postponed after clashes between Shia fighters and Iraqi security forces.
In November, parliament approves a security pact with the US which says that all US troops will leave the country by the end of 2011.
The new US embassy in Baghdad opens officially, as private security contractor Blackwater is banned from the country.
A Baghdadi criminal court sentences the journalist who threw a shoe at the US president is sentenced to three years.
Iraq takes more and more control of key areas, including Baghdad’s Green Zone.
President Maliki’s party scores big gains in provincial elections.
US President Barack Obama announces the withdrawal of most US troops from Iraq by August 2010. Troops withdraw from towns and cities; but some will stay on to advise the Iraqi security forces until final withdrawal in 2011.
Britain officially ends combat operations in southern Iraq. They hand control of their Basra base over to US forces.
An independent inquiry into the Iraq war begins in London.
Barzani is re-elected in a presidential election, and the governing alliance retains its position despite new opposition parties gaining added support.
Prime Minister Maliki also announces the State of Law, a grouping of 40 political parties, after a split in the United Iraqi Alliance.
Britain's Shell and Malaysian firm Petronas are awarded a joint contract to exploit Iraq's giant Majnoon oil field, potentially worth $12bn.
‘Chemical’ Ali Hassan al-Majid, who was a key figure in Saddam’s government, is executed.
Parliamentary elections are held in March and no coalition wins enough votes for a majority as Iraq's neighbours anxiously eye the voting.
Al-Qaeda in Iraq leaders are hunted down and killed by an Iraqi intelligence team.
Iraq’s leading army official criticises the planned withdrawal of US troops, saying that Iraq may not be ready for the move. The last US combat brigade leaves Iraq in August, but 50,000 troops remain for training and advisory purposes.
Wikileaks publishes thousands of classified US military logs on the war in Iraq.
The two main political blocs end talks on forming an alliance government.
In November, Jalal Talabani is appointed as president and Nouri al-Maliki as prime minister. Parliament approves a new government that includes the major factions.
Amid worsening violence, an Iraqi church attack in Baghdad that kills 58 people is claimed by al-Qaeda.
Moqtada al-Sadr returns to Iraq after years of self-imposed exile in Iran.
Thousands gather in Baghdad and northern Iraq demanding improved services and an end to corruption, apparently inspired by the Arab Spring protests that have spread across the region.
The Iraqi government plans a summit to decide whether US troops are needed in the country past the 2011 withdrawal deadline, as US officials continue to advocate for a future presence.
Al-Sadr says his fighters will suspend miltary attacks on the US, which will resume only if the US fails to pull out in time.
In October, US officials announce they have abandoned plans to keep troops in Iraq and will leave by the end-of-year withdrawal deadline.
As the drawdown looms, Iraq's prime minister visits the US to chart future relations.