The 1st Battalion, 121st Field Artillery is currently part of the 157th Maneuver Enhancement Brigade that is based out of Milwaukee, Wisconsin. Attached to the 1-121st is Battery A located in Sussex, Wisconsin; Battery B located in Plymouth, Wisconsin; 108th Forward Support Company located in Sussex, Wisconsin. The 1-121st FA originally operated M101 howitzer before switching to the M270 Multiple Launch Rocket System (MLRS) in 2003. As of 2010 the 1-121st FA operates the M142 High Mobility Artillery Rocket System (HIMARS).