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.
The majority Shia population, which had been excluded from power, was initially jubilant at the 2003 campaign to remove Saddam Hussein/
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.
By early 2014, Sunni rebels led by the extreme jihadist group calling itself Islamic State (IS) had established strongholds in the mainly Sunni Anbar Province.
Army resistance quickly melted away, and within months, IS fighters had begun to move into central and northern Iraq, threatening the unity of the state.
A US-led coalition of regional and Western powers responded with a campaign of air strikes, as the Iraqi government attempted to group.
After elections in 2014, Shia-dominated government of Prime Minister Nouri al-Maliki with replaced the less divisive figure of Haider al-Abadi and a new broad-based government including Sunni Arabs and Kurds in September 2014.
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.
The area threatened to hold a referendum on independence after the seizure of northern Iraq by IS militants in 2014, but backed down after the creation of more broad-based government in Baghdad.