The Second Battle of Fallujah, codenamed Operation Phantom Fury, and Operation al-Fajr (الفجر, The Dawn), was an American-led offensive of the Iraq War that lasted roughly six weeks, starting 7 November 2004. Marking the highest point of the conflict against the Iraqi insurgency, it was a joint military effort carried out by the United States, the Iraqi Interim Government, and the United Kingdom. Within the city of Fallujah, the coalition was led by the U.S. Marine Corps and U.S. Army, the battle was later described as "some of the heaviest urban combat U.S. military have been involved in since the Battle of Huế City in Vietnam in 1968".
Operation Phantom Fury was the second major coalition effort in Fallujah. Earlier, in April 2004, coalition forces fought the First Battle of Fallujah in an attempt to capture or kill insurgent elements who were considered responsible for the 2004 Fallujah ambush, which resulted in the deaths of four private military contractors of Blackwater. When the coalition fought their way into the centre of the city, the Iraqi Interim Government requested that the city's control be transferred over to an Iraqi-run local security force, which then began stockpiling weapons and building complex defenses across the city through mid-2004. The Second Battle of Fallujah was the bloodiest battle of the entire conflict for American troops, and is notable for being the first major engagement of the Iraq War that was fought solely against insurgents as opposed to the government military forces of the former Ba'athist Iraq.
In February 2004, control of Fallujah and the surrounding area in the Al Anbar Governorate was transferred from the U.S. 82nd Airborne Division to the 1st Marine Division. Shortly afterward, on 31 March 2004, four American private military contractors from Blackwater – Wesley Batalona, Scott Helvenston, Jerry Zovko, and Michael Teague – were ambushed and killed in the city. Images of their mutilated bodies were broadcast around the world.