Iraq, in an area once home to some of the earliest civilisations, became a battleground for competing forces after the US-led ousting of President Saddam Hussein in 2003.
The Shia-led government struggled to restore order until a "surge" of US troops in late 2007 began to push insurgents and militias out of cities and provinces they had long contested.
The country remains volatile, and disputes with the autonomous Kurdistan Region over the oil-rich city of Kirkuk have threatened to derail progress towards political stability. Sunni Muslim insurgents continue to use violence in an effort to undermine the Shia-dominated government.
The 2003 campaign to remove Saddam Hussein began with a US missile attack on Baghdad in the early hours of 20 March. US and British forces invaded from the south days later.
At a glance
- Politics: Iraq became a battleground for forces vying for power after the US-led invasion of 2003, and an uneasy Shia-led government took over when US forces left in 2011
- Security: Unity government and US-led coalition forces made progress in establishing control after thousands of civilians were killed in rebel-orchestrated violence. Bomb attacks, mainly against Shias, increased through 2013
- Economy: Violence and sabotage has hindered efforts to revive an economy shattered by decades of conflict and sanctions; Iraq has the world's third largest reserves of crude oil but attacks, corruption and smuggling have crippled exports
Country profile compiled by BBC Monitoring
Only three weeks after the start of the fighting, they had entered Baghdad, and the Iraqi leader's grip on power had withered. The majority Shia population, which had to a large extent been excluded from power, was initially jubilant.
However, optimism gradually gave way to despair as insurgent groups - mainly drawn from embittered Sunnis, dismissed army officers and supporters of the former regime - began an increasingly bloody campaign of bomb attacks.
The insurgents - with al-Qaeda in Iraq among the most violent - targeted civilians as well as security forces, at times killing hundreds of people in one day. The conflict descended into near sectarian warfare in 2006-7 when Shia militant groups struck back with a campaign of kidnappings and killings.
The transfer of power to an interim Iraq government in June 2004, and seven months later, Iraq's first multi-party elections in 50 years, which brought an overwhelmingly Shia-dominated coalition to power, failed to stem the violence.
By 2008, however, a "surge" in US troop levels to confront the insurgents, the co-opting of moderate Sunni tribesmen in the struggle against militants and an improving Iraqi army had succeeded in turning the situation around. The number of attacks lessened. However, sectarian violence had gathered pace again by early 2013.
In June 2009 US troops withdrew from Iraq's towns and cities, handing over security to Iraqi forces. In line with a pledge by US President Barack Obama the last US combat troops left Iraq in August 2010. The last US troops left Iraq by the end of 2011.Cradle of civilisation
Straddling the Tigris and Euphrates rivers and stretching from the Gulf to the Anti-Taurus Mountains, modern Iraq occupies roughly what was once ancient Mesopotamia, one of the cradles of human civilisation.
In the early Middle Ages, Iraq was the heartland of the Islamic Empire, but a brutal Mongol invasion in the 13th century destroyed its importance. Part of the Ottoman Empire from the 15th century, it came under British control after World War I, gaining independence in 1932.
The British-installed monarchy was toppled in 1958 and a coup in 1968 brought the Arab nationalist Ba'ath (Renaissance) party to power. Oil made the country rich, and when Saddam Hussein became president in 1979, petroleum made up 95% of its foreign exchange earnings.
But the 1980-88 war with Iran and the 1991 Gulf War, sparked by Iraq's invasion of Kuwait, together with the subsequent imposition of international sanctions, had a devastating effect on its economy and society.
What remained of the economy was largely shattered by the 2003 invasion and the subsequent violence. Attacks by insurgents on Iraq's oil infrastructure cost the country billions of dollars in lost revenues.
In the north, the Kurdish community has managed to create an autonomous region of its own.