The battalion deployed in June 2004 to Iraq as a part of Regimental Combat Team 1 and later RCT-7, 1st Marine Division (Reinforced). From June 2004 to January 2005, 1/8 conducted combat operations in Al Anbar Province in Area of Operations (AO) Denver and later AO Raleigh, including operations in Rawa, Anah, Little Anah, Haditha, Baghdadi, Barwana, Abu Buyatt, ASP Wolf, Hit, Al Asad, Haqlanyih, Karmah, Naser Wa Saleem, Abu Ghuraib, and Fallujah. 1st Battalion 8th Marines was one of the lead battalions during Operation Phantom Fury from 8 November to 9 December 2004 leading the assault into Fallujah. During combat operations in Iraq from June 2004-January 2005, 1st Battalion 8th Marines (Reinforced) suffered 21 Marines killed in action (KIA) and nearly 150 Marines wounded in action (WIA) with 17 KIA's and 102 WIA's coming in three weeks in Fallujah in November 2004. 1/8 conducted a relief in place with their sister battalion 3/8 and returned to Camp Lejeune by 1 February 2005.