Falluja - a predominantly Sunni Muslim city 50km (30 miles) west
of Baghdad - has had a long history as a rebellious city.
Falluja was pounded by a steady US bombardment
Before a military assault on the city in November left much of it in ruins, the city was believed to be the centre of the insurgency against US forces and the Iraqi government. It was one of the main obstacles to the US and Iraqi efforts to pacify Iraq.
The most wanted man in Iraq, Abu Musab al-Zarqawi, was said to be hiding out with his bands of suicide bombers and hostage-takers. It was also a stronghold of Saddam Hussein loyalists.
Falluja was also supposed by many to be where the dozens of foreigners taken hostage in Iraq have been kept captive.
In November, arguing that Iraq's Sunnis would not be able to participate in elections scheduled for January because of the security situation in Falluja, US and Iraqi officials ordered a major offensive against the city. The aim was to flush out the insurgents and bring the city within the control of the Iraqi interim government.
Most of the city's population of between 250,000 and 300,00 fled before or during the fighting and took refuge in towns and villages nearby.
After weeks of fierce fighting, US troops captured most of the city, although they were still encountering pockets of resistance in December.
US officials acknowledge that while the effect of the Falluja operation has been to weaken the insurgency, it had not eliminated it. Insurgents that were not captured or killed have spread out and moved on to other areas.
Some of Falluja's inhabitants have begun to return but much of the city lies in ruins and there is no running water or electricity.
Military officials now face the challenge of winning back the confidence of people whose city they have just destroyed.
The plan is to begin reconstruction work quickly. Badly damaged homes will be bulldozed and rebuilt and many home owners will be compensated. According to reports, there are plans for a new wastewater treatment plans, new schools and health clinics.
American officials say they will provide money and expertise to rebuild the city but the Iraqi interim government should make the major decisions.
The US hopes to put Iraqi security services in charge of Falluja in time for the elections due on 30 January but it remains to be seen how many of the residents will be able to return in time for the poll.
There are also fears that insurgents could filter back into the city and try to sabotage the rebuilding efforts.
Falluja is known as the "city of mosques" because of the 200 or more found in and around the area.
Under the patronage of Saddam Hussein, and on the back of oil wealth, it grew from a marginal town under the Ottoman empire to an influential base for the Baathist regime.
But US officials and Iraqi Prime Minister Iyad Allawi said it had become a safe haven for foreign fighters, who have crossed into Iraq intent on attacking "occupation" forces.
Falluja had been in rebel hands since shortly after US forces handed responsibility for security to Iraqi forces in April.
But it had been a trouble spot for the US long before.
There are two schools of thought as to why.
One is that here was one of the main strongholds of support for Saddam Hussein, an area where the old regime strove hard to win the allegiance of powerful tribal groupings through power and patronage.
But another school of thought says that here the American forces squandered most quickly any goodwill they may have garnered from liberating the country from a cruel dictatorship.
April 2003: US paratroopers shoot dead 13 demonstrators
May 2003: attacks on US troops become a routine occurrence
Nov. 2003-Jan. 2004: attacks on three US helicopters kill 25
Feb. 2004: 25 killed in attacks on Iraqi police
31 Mar 2004: four US contractors killed
Apr 2004: US seals off city
May 2004: Siege lifted
June 2004: Zarqawi loyalists targeted in US raids - continuing to date
Oct 2004: Iraqi PM threatens military action if Zarqawi is not handed over
On the night of 28 April 2003, for example, members of the 82nd Airborne Division opened fire on a demonstration in Falluja, killing 13 people.
Two more were killed in similar circumstances a couple of days later.
US forces say they came under fire from the crowd, but local residents say their was no firing from the crowd and neither march posed any threat to US forces.
Within days seven members of the 82nd Airborne Division were injured in a grenade attack on their compound in Falluja.
An unknown number of Iraqis have also been killed by the Americans, including insurgent fighters, passing civilians and policemen apparently hit by "friendly fire".