Direct proof of use
The B-52H Stratofortress was used by U.S. forces during Operation Iraqi Freedom. The U.S. Air Force fact sheet says the aircraft launched approximately 100 Conventional Air-Launched Cruise Missiles during a night mission on March 21, 2003.
A separate Air Force report from April 12, 2003 documents a B-52 using a Litening II targeting pod in combat for the first time, striking targets at an airfield in northern Iraq on April 11 with two GBU-12 Paveway II laser-guided bombs.
Sources: B-52H Stratofortress | U.S. Air Force, B-52 Litening II Pod Used in Combat
Timeline
The campaign-level air component report dates the large-scale coalition air strikes against Iraq to March 21, 2003 at 1800Z and counts more than 1,700 air sorties, including 504 TLAM and CALCM cruise missiles, in that opening phase.
By April 10, 2003, B-52H crews had reached more than 100 missions in support of Operation Iraqi Freedom. An Air Force account of that milestone describes the 100th mission as a strike against regime fortifications north of Baghdad.
Sources: Operation Iraqi Freedom: By the Numbers, B-52 Still a Force to Be Reckoned With
Operational role
The documented Iraq use combined long-range standoff attack, strategic bombing, and direct support to coalition ground operations. The Air Force described B-52 OIF missions as ranging from strategic attack to close air support, with targets communicated through command nodes and coalition ground forces.
The April 11 Litening pod strike showed the B-52 being adapted for more flexible precision attack. The Air Force report identified a mixed Reserve and active-duty crew flying from a forward-deployed location and using the pod to designate targets for laser-guided weapons without relying on another aircraft or ground designator.
The available public sources support specific dated missions and aggregate campaign milestones. They do not provide a complete sortie-by-sortie public history of every B-52 mission flown during the 2003-2011 Iraq War.
Sources: B-52 Still a Force to Be Reckoned With, B-52 Litening II Pod Used in Combat, Operation Iraqi Freedom: By the Numbers