The Commanding Officer of the Wisconsin Artillery, Colonel Philip C. Westfahl, became Commander of the new regiment. On September 19, 1917, the Regiment was re-designated as the 121st Field Artillery Regiment and assigned to the 57th Field Artillery Brigade as a part of the 32nd Division. In addition to the 32nd Division, the records indicated the 121st Field Artillery Regiment also supported the 3rd, 47th, 79th, and the regiment distinguished itself in six major campaigns: Aisne-Marne, Alsace, Champagne, Lorraine, Meuse-Argonne, and Oise-Aisne. Along with the General of the Armies John J. Pershing's personal commendation, the regiment received the battle streamer of the French Croix-de-Guerre with Silver Star embroidered Aisne-Marne and Oise-Aisne. The 121st Field Artillery Regiment was demobilized at Camp Grant, Illinois., May 17, 1919. On February 1, 1942, the 32nd Division was converted from "square" configuration to "triangular" and re-designated as the 32nd Infantry Division. Under the Division reorganization, the 121st Field Artillery Regiment was divided. The Regimental headquarters became the HQs for the 173rd Field Artillery Regiment, the 1st Battalion was redesignated as the 121st Field Artillery Battalion and the 2nd Battalion became the 1st Battalion 173rd Field Artillery Regiment. In February 1943 the 173rd Field Artillery Regiment would undergo further re-organizations, with the Regimental HQs becoming the 173rd Field Artillery Group and the 1-173rd being redesignated as the 985th Field Artillery Battalion, and the 2-173rd being redesignated as the 173rd Field Artillery Battalion. The 121st Field Artillery Battalion, as designated on February 1, 1942, distinguished itself in the Pacific Theatre of Operations. Its honors were: Aitape, Biak, Leyte, Luzon and New Guinea (with Saidor Arrowhead). Early in 1943 the 121st Field Artillery Battalion was issued 75 mm howitzers in place of the 155 mm howitzers that were its normal weapons as the general support battalion of Division Artillery. The 173rd Field Artillery Group, as designated in February 1943, distinguished itself in the European Theatre of Operations. Its honors were: Normandy, Northern France, Ardennes-Alsace and Central Europe.