World War II

203rd Field Artillery Group Headquarters, European Theater
(c) 152nd Field Artillery Association, 2011
152nd Field Artillery Association
In the aftermath of the triangularization of the Army's Infantry Divisions, the 152nd Field Artillery was redesignated as the 203rd Field Artillery in February 1942, consisting of two subordinate battalions, the 1st (formerly the 1st Bn, 152nd FA) and 2nd (formerly the 1st Bn, 192nd FA). Just a year later in March 1943 they were reorganized as the 203rd Field Artillery Group; the subordinate battalions went their separate ways.
The 203rd Field Artillery Group HQ was initially commanded by the former 152nd FA regimental commander COL John F. Choate, but sometime between January and July 1943 the command changed to James M. Lewis and then, by July 1944, to John C. Butner, Jr., a regular army officer. By December of 1944 the final commander, Donald B. Harriott, who had been the Executive Officer under the previous commanders, took command.
The Group HQ hit Utah Beach in France on 3 and 4 September, 1944 and fought with Patton's Third Army for much of the rest of the war. We're fortunate to have copies of the Group's official After Action Reports thanks to MSgt James Earl Downes, one of the few Maine men who were part of the 152nd FA Regimental Headquarters prior to the 1941 mobilization and remained through the end of the war. The AARs were provided to the Association by MSgt Downes' son, Richard Downes.
MSgt. James Earl Downes, Communications Chief, 203rd Field Artillery Group, Brettnach, France, Nov. 27, 1944
203rd Field Artillery Group WW2 After Action Reports
The following units were attached to the 203rd FA Group for some period of time, and are mentioned in the After Action Reports (in the order mentioned):

739th Field Artillery Battalion (commanded by Herbert M. Brown, a 152nd vet)
989th Field Artillery Battalion
999th Field Artillery Battalion
270th Howitzer Battalion (commanded by James C. Gabriel)
277th Howitzer Battalion (commanded by Wayne A. Gudmonson)
243rd Field Artillery Battalion
733rd Field Artillery Battalion (commanded by Calvin C. Seavey)
176th Field Artillery Battalion
177th Field Artillery Battalion
731st Field Artillery Battalion
578th Field Artillery Battalion
257th Field Artillery Battalion
514th Field Artillery Battalion
949th Field Artillery Battalion
687th Field Artillery Battalion
559th Field Artillery Battalion
76th Field Artillery Battalion
191st Field Artillery Battalion
955th Field Artillery Battalion
734th Field Artillery Battalion
253rd Armored Field Artillery Battalion
Good Conduct Medal Orders, 1943-1945. Incomplete, but this is everything that the National Archives has.
Brief 203rd FA Regiment history from an article for publication at Ft. Bragg in February 1943.