The US-led invasion of Iraq that toppled Saddam Hussein aimed to enshrine a liberal democracy in the heart of the Middle East but instead unleashed sectarian violence and endless political disputes.

Launched a decade ago with the stated goal of wiping out Saddam's stores of weapons of mass destruction, which were never found, the focus of the divisive war quickly shifted to solidifying Iraq as a Western ally in an unstable region.

But the removal of Saddam gave Iraq's non-Arab neighbour Iran the opportunity to dramatically increase its sway in the country, with ambiguous motives, according to Western diplomats.

And since the departure of American forces at the end of 2011, Washington has often struggled to exert influence over Baghdad.

"There were the superficial arguments -- the weapons of mass destruction, the links with Al-Qaeda, the present risks to the security of the United States," said Crispin Hawes, London-based Middle East and North Africa director for the Eurasia Group consultancy.

"These things look farcical now."

And there was "the underlying argument... that Iraq would be not only a US ally, but the rapid recovery of the Iraqi economy would provide an engine of growth not just for Iraq but for the rest of the region, and provide a sort of exemplar for the region," he added.

"These things look horribly ironic now."

Though the war itself was relatively brief -- it began on March 19, 2003, Baghdad fell on April 9, and then-US president George W. Bush infamously declared the mission accomplished on May 1 -- its aftermath was violent and bloody.

Insurgents carried out increasingly frequent bombings and shootings, and Iraq erupted into sectarian bloodshed that left tens of thousands dead following a February 22, 2006 attack on a Shiite shrine in Samarra.

A mostly American coalition, albeit with significant long-term contributions from Britain in particular, regularly battled Sunni and Shiite insurgents nationwide, from the Sunni bastions of Fallujah and Mosul to the Shiite cities of Najaf and Basra.

Since the invasion, at least 110,000 Iraqi civilians, several thousand more policemen and soldiers, and 4,800 foreign troops -- the vast majority of them American -- have died in the carnage.

Violence, which remains high by international standards, was only brought under some measure of control from 2008 onwards, as the American troop "surge" coincided with Sunni tribal militias deciding to side with US forces.

But political reconciliation, the strategic goal of the surge, was never fully achieved.

From territorial disputes in the north to questions over the apportioning of the country's vast energy revenues, a number of high-level problems remain unresolved, while Iraqis still grapple with daily struggles ranging from poor provision of basic services to high levels of unemployment.

-- Oil bright spot --

And though violent sectarian conflict is largely a thing of the past, minority Sunnis, empowered during Saddam's rule, have for months held regular mass rallies against the alleged targeting of their community by the Shiite-dominated authorities.

Prime Minister Nuri al-Maliki's erstwhile government partners, meanwhile, have charged him with consolidating power over the bureaucracy and security forces, and little in the way of landmark legislation has been passed in recent years.

The two factors have collided with Finance Minister Rafa al-Essawi, a top Sunni leader and member of the Sunni-backed Iraqiya bloc, announcing his resignation at an anti-government protest, while the demonstrations have entered their third month.

Key laws regulating the lucrative energy sector, the funding of political parties, a proposed amnesty for non-violent criminals, and others have all languished for months and, in some cases, years.

Through it all, however, a major bright spot has been Iraq's booming oil sector, which has boosted the government's coffers and is projected to expand still further.

The International Energy Agency estimates Iraq will make by far the biggest contribution to oil production increases in the coming decades.

Authorities have voiced ambitious plans to use the funds on a variety of projects -- a massive housing project on Baghdad's outskirts, a new airport near Najaf, and a world-class football stadium in the southern port city of Basra.

But the rising revenues, which have already pushed Iraq's budget to greater than that of Egypt, a country with more than twice the population, have yet to result in visibly higher living standards, due largely, analysts say, to bureaucratic incompetence and rampant corruption.