linguistic:paraphrasing
2004: Insurgency expands

The start of 2004 was marked by a relative lull in violence. Insurgent forces reorganised during this time, studying the multinational forces' tactics and planning a renewed offensive. However, violence did increase during the Iraq Spring Fighting of 2004 with foreign fighters from around the Middle East as well as Jama'at al-Tawhid wal-Jihad, an al-Qaeda -linked group led by Abu Musab al-Zarqawi, helping to drive the insurgency.

As the insurgency grew there was a distinct change in targeting from the coalition forces towards the new Iraqi Security Forces, as hundreds of Iraqi civilians and police were killed over the next few months in a series of massive bombings. An organized Sunni insurgency, with deep roots and both nationalist and Islamist motivations, was becoming more powerful throughout Iraq. The Shia Mahdi Army also began launching attacks on coalition targets in an attempt to seize control from Iraqi security forces. The southern and central portions of Iraq were beginning to erupt in urban guerrilla combat as multinational forces attempted to keep control and prepared for a counteroffensive.

The most serious fighting of the war so far began on 31 March 2004, when Iraqi insurgents in Fallujah ambushed a Blackwater USA convoy led by four US private military contractors who were providing security for food caterers Eurest Support Services. The four armed contractors, Scott Helvenston, Jerko Zovko, Wesley Batalona, and Michael Teague, were killed with grenades and small arms fire. Subsequently, their bodies were dragged from their vehicles by local people, beaten, set ablaze, and their burned corpses hung over a bridge crossing the Euphrates. Photos of the event were released to news agencies worldwide, causing a great deal of indignation and moral outrage in the United States, and prompting an unsuccessful "pacification" of the city: the First Battle of Fallujah in April 2004.

The offensive was resumed in November 2004 in the bloodiest battle of the war: the Second Battle of Fallujah, described by the US military as "the heaviest urban combat (that they had been involved in) since the Battle of Hue City in Vietnam." During the assault, US forces used white phosphorus as an incendiary weapon against insurgent personnel, attracting controversy. The 46‑day battle resulted in a victory for the coalition, with 95 US soldiers killed along with approximately 1,350 insurgents. Fallujah was totally devastated during the fighting, though civilian casualties were low, as they had mostly fled before the battle.

Another major event of that year was the revelation of widespread prisoner abuse at Abu Ghraib, which received international media attention in April 2004. First reports of the Abu Ghraib prisoner abuse, as well as graphic pictures showing US military personnel taunting and abusing Iraqi prisoners, came to public attention from a 60 Minutes II news report (28 April) and a Seymour M. Hersh article in The New Yorker (posted online on 30 April). Military correspondent Thomas Ricks claimed that these revelations dealt a blow to the moral justifications for the occupation in the eyes of many people, especially Iraqis, and was a turning point in the war.

2004 also marked the beginning of Military Transition Teams in Iraq, which were teams of US military advisors assigned directly to New Iraqi Army units.