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 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.
And since the departure of American forces at the end of 2011, Washington has often struggled to exert influence over Baghdad.
Iraqi officials have not announced any ceremonies to mark the anniversary on Wednesday, with events more likely to be held on April 9 to mark the day Baghdad fell.
Though the war itself was relatively brief -- it began on March 20, 2003, Baghdad fell weeks later, 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.
Since the invasion, at least 112,000 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.
Prime Minister Nuri al-Maliki's erstwhile government partners, meanwhile, have charged him with monopolising power, and little in the way of landmark legislation has been passed in recent years.
Through it all, however, a bright spot has been Iraq's booming oil sector, which has boosted the government's coffers and is projected to expand still further.
Authorities have voiced ambitious plans to use the funds on a variety of projects -- a massive housing plan for 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.