Direct proof of use
CAESAR use in the 2014 War Against the Islamic State is documented through official coalition reporting on French Task Force Wagram, the French artillery detachment deployed under Operation Chammal in support of Operation Inherent Resolve.
Combined Joint Task Force - Operation Inherent Resolve said Task Force Wagram integrated into the coalition fire-support system from 2016 and fought from Mosul to Baghouz. The same account described the deployment as the largest external-operation engagement of CAESAR artillery guns and reported more than 2,500 fire missions.
Sources: Task Force Wagram Dissolution, Task Force Wagram Hajin
Timeline
Task Force Wagram's coalition artillery role began in 2016. DVIDS imagery from 16 May 2018 placed French soldiers assigned to the task force at Al Qaim, Iraq, loading and firing French CAESAR guns during Operation Roundup.
In January 2019, CENTCOM reported that Task Force Wagram was supporting Syrian Democratic Forces ground troops in the Middle Euphrates River Valley and that French artillery helped stop Islamic State attacks around Hajin in December 2018. On 29 April 2019, the task force held its dissolution ceremony at Al Asad Air Base, Iraq.
Sources: Task Force Wagram Dissolution, Task Force Wagram Hajin, DVIDS French Caesars Loading, DVIDS French Caesars Fire Mission
Narrative
In this conflict, CAESAR served as a coalition ground-fire system rather than as a transferred partner-force weapon. French troops operated the guns from Iraq while supporting Iraqi and Syrian partner-force operations against Islamic State positions.
The best documented employment was Task Force Wagram's fire-support role for Operation Roundup and the Middle Euphrates River Valley campaign. Official reporting describes the detachment as part of the coalition fire-support architecture, supporting Syrian Democratic Forces around Hajin and participating across battles from Mosul to Baghouz before the task force dissolved in April 2019.
The public sources used here establish deployment, operation, firing missions, and fire-support effects, but they do not provide a complete target-by-target firing log or munition inventory for Task Force Wagram.
Sources: Task Force Wagram Dissolution, Task Force Wagram Hajin, DVIDS French Caesars Loading, DVIDS French Caesars Fire Mission