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 governments that have held power since then have struggled to maintain order, and the country has enjoyed only brief periods of respite from high levels of sectarian violence.
A Sunni Muslim insurgency increased in intensity following the withdrawal of the last US troops in 2011, and by mid-2013 the country was described as being in the grip of a full-blown sectarian war again.
By early 2014, Sunni rebels led by the Islamic State of Iraq and the Levant (ISIS) had established strongholds in the mainly Sunni Anbar Province. Within months, Islamic State had begun to move into central and northern Iraq, threatening the unity of the state.
The autonomous Kurdistan Region initially responded to the threat posed by Islamic State by announcing plans to hold a referendum on independence, on the grounds that Iraq was already "effectively partitioned".
However, following the replacement of Iraqi Prime Minister Nouri al-Maliki with the less divisive figure of Haider al-Abad and the formation of a new broad-based government including Sunni Arabs and Kurds in September 2014, the Iraqi Kurdistan independence referendum was put on hold.
At a glance
- Politics: Iraq became a battleground for forces vying for power after the US-led invasion of 2003, and governments have struggled to hold the country together since US forces left in 2011
- Security: Sunni attacks on Shias through 2013 erupted into full-scale insurrection the following year
- Economy: Violence and sabotage hinder the revival of 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
Profile of Iraqi Kurdistan
The 2003 campaign to remove Saddam Hussein took three weeks to capture Baghdad. The majority Shia population, which had been excluded from power, was initially jubilant, but 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 acquired a marked sectarian aspect in 2006-7 when Shia militant groups struck back with a campaign of kidnappings and killings.
The transfer of power to an interim government in June 2004 and, seven months later, the 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 rebels, the co-opting of moderate Sunni tribesmen in the struggle against militants, and an improving Iraqi army succeeded in turning the situation around.
In June 2009 US troops withdrew from Iraq's towns and cities, and the last remaining US forces left the country at the end of 2011. But the Shia-led government of Nouri al-Maliki failed to unite Iraq's various communities and from 2013 faced a rapidly-rising tide of extreme Sunni rebellion in Anbar Province.
In the summer of 2014 the rebels broke through to central Iraq, bringing down the government and forcing the authorities to turn to the US, Iran and Kurdish forces for help.
An international conference in Paris pledged a new forward strategy against the self-proclaimed 'Islamic State' Sunni insurgency, and included ten Sunni Arab states - but not Syria or Iran.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, and is pushing for greater territory and more powers.