The United States bombardment of Fallujah began in April 2003, one month after the beginning of the invasion of Iraq. In April 2003 United States forces fired on a group of demonstrators who were protesting against the US presence. US forces alleged they were fired at first, but Human Rights Watch, who visited the site of the protests, concluded that physical evidence did not corroborate US allegations and confirmed the residents' accusations that the US forces fired indiscriminately at the crowd with no provocation. 17 people were killed and 70 were wounded. In a later incident, US soldiers fired on protesters again; Fallujah's mayor, Taha Bedaiwi al-Alwani, said that two people were killed and 14 wounded. Iraqi insurgents were able to claim the city a year later, before they were ousted by a siege and two assaults by US forces. These events caused widespread destruction and a humanitarian crisis in the city and surrounding areas. As of 2004, the city was largely ruined, with 60% of buildings damaged or destroyed, and the population at 30%–50% of pre-war levels.

The First Battle of Fallujah, code-named Operation Vigilant Resolve, was an operation against militants in Fallujah as well as an attempt to apprehend or kill the perpetrators of the killing of four U.S. contractors in March 2004.