Direct proof of use
DVIDS-derived public-domain records document U.S. Marines with Task Force Southwest firing 120 mm mortar illumination rounds at Bost Airfield, Afghanistan, during April 2018. One record describes an April 5 fire mission that helped enable Afghan National Defense and Security Forces during constant combat operations in Helmand Province. A second record documents April 24 firing from the same airfield to support Afghan security-force maneuvers during combat operations in Helmand.
Sources: Bost Airfield April 5 Illumination Fire Mission, Bost Airfield April 24 Illumination Fire Mission
Narrative
In this Afghanistan use case, the munition served as battlefield illumination rather than as a casualty-producing round. The recorded users were U.S. Marines assigned to Task Force Southwest, and the supported force was the Afghan National Defense and Security Forces.
Both source records place the use in Helmand Province during the Resolute Support and Operation Freedom's Sentinel period of the war. The available public records identify the ammunition class and support purpose, but they do not identify a specific 120 mm illumination cartridge model such as M930 or M983.
Sources: Bost Airfield April 5 Illumination Fire Mission, Bost Airfield April 24 Illumination Fire Mission