This United States Army publication, Training Circular TC 3-22.90 Change 1 Mortars December 2022, prescribes guidance for leaders and members of mortar squads. It presents practical solutions to assist in the timely delivery of accurate mortar fires, for mortar squad training. The scope of this publication includes mortar squad training at the squad level. The 60-milimeter (mm) mortar, M224/M224A1; 81-mm mortar, M252/M252A1; 120-mm mortars, M120/M121; and the Recoil Mortar System 6–Lightweight (RMS6-L) are discussed, and includes nomenclature, sighting, equipment, characteristics, capabilities, and ammunition.