Corps, Attached units, US Army

I found this:

Here:
http://www.militaryhistoryonline.com/wwii/usarmy/artillery.aspx

This one:
http://www.90thdivisionassoc.org/afteractionreports/PDF/XIICorpsHist.pdf
Has some general information as well as detailed information at several points in time for 12th corp.
This document (see page 351 and on specifically) may help:
http://www.history.army.mil/html/books/002/2-1/CMH_Pub_2-1.pdf
This one has some detailed info for the ones in the Pacfic:
https://archive.org/details/OrderOfBattleUsArmyPtoWw2
Not what you asked for but then there is NARA 338.10.1
https://www.archives.gov/research/guide-fed-records/groups/338.html
Which probably has more details than anyone sane really wants.

Page 354 of this document may be what you are looking for (and it may duplicate one of the above):
http://www.history.army.mil/html/books/002/2-1/CMH_Pub_2-1.pdf

 

Even leaner than you might imagine from that listing. Technically, in the U.S. Army, the corps consisted of a small number of units assigned to the headquarters and a large number of attachments from army dependent on the army commanders intent. In essence it was:

Corps HQ, consisting of:

HQ Company
HQ & HQ Battery, Corps Artillery
HQ Detachment, Special Troops ([SIZE=10pt]The “Special Troops” detachment in an army or corps headquarters was “to direct and supervise both tactical and administrative instruction and training of its component units, with the exception of divisions, brigades and groups.” )[/SIZE]
Corps MP Platoon
Provisional Counterintelligence Corps Detachment
Special Services Company ([SIZE=10pt]The Special Service Company provided “recreational and informational services to troops serving in a theater of operations”. )[/SIZE]

Assigned Corps Troops ([SIZE=10pt]Corps Troops included units assigned to the corps as well as army and corps troops attached to the corps and its assigned units. Attached Troops included army and corps troops attached for operations .) [/SIZE]
Typically, assigned corps troops included:

Signal Battalion
Signal Service Company (Radio Intercept)
Field Artillery Observation Battalion
HQ & HQ Battery, AAA Group plus attached AAA battalions
HQ & HQ Company, Engineer Combat Group plus attached Engineer battalions and companies
HQ & HQ Detachment, Medical Battalion, plus attached Medical companies and detachments
HQ & HQ Detachment, Ordnance Battalion, plus attached Ordnance companies and detachments
Corps Machine Records Unit
Platoon, QM Car Company

Everything else was an attachment from army.

 

You need to get Rich's attention again ....

 

I think the answer is in your initial question. Corps are a fluid organization assigned to a sector. What they were assigned was what Army thought needed in that sector, how those miscellaneous units were deployed were up to the Corps Commander. In much of my reading, dealing with XIX Corps, they were often stripped down to just 30th ID and 2nd AD, yet it becomes obvious that even stripped down to 2 Divisions, you had all the support elements coming through Corps; those units forgotten in the written history; Transportation Companies, Graves Registration, Military Police, Field Artillery Observation Battalions, Repair units for both armor and vehicles, etc, etc.

You also see elements of many other attached units formed into battle groups when required. A good example is in 30th ID at Stavelot-LaGlieze - as oddball units came into the sector under Corps control, they were formed into battle groups named after the senior officer. You had companies and battalions from many different units, both armored and infantry, just tossed together into three different battle groups descending on LAH from the north, northwest, northeast. All of this supported by artillery which was also a hodge-podge of units assigned into the sector because of the crisis.

The corps concept is an interesting and very thoughtful strategy. At times, for an attack, you good pre-load the lead Corps with as many Divisions and special units as needed, but you could also add elements to a Corps defending a sector under unexpected attack with any unit in the area, and that seemed to work with minimal confusion.

So, while a Corps might have a minimal number of fighting and support units permanently assigned, they were also a dynamic element that could absorb and direct other added units on the fly, with (seemingly) minimal confusion.

 

Sorry, been busy.

Okay, first, a minor correction. VIII Corps did not "turn north". It was the corps on which the attack initially fell. The corps HQ withdrew south from Bastogne to Neufchatel and was eventually attached to Third Army, which had been its original parent. The initial "movement" north by Third Army was by XII Corps, which handed off most of its units to XX Corps before taking command of the 4th ID, 10th AD, and elements of 9th AD and 28th ID from VIII Corps in place. As they came up it then took command of the 5th ID. Further west, III Corps, which was newly arrived and uncommitted in reserve, was assigned the 4th AD, 26th ID, and 80th ID as they came up from the former XII Corps zone. Both corps then began the initial Third Army counterattacks on 7. Armee. VII Corps in the north executed a similar movement.

As far as tactical and administrative movement coordination, that was a major function of the G3/S3 shop at each level of command. Roads were assigned within army, corps, and division based upon trafficability and road space as determined by maps and engineer reconnaissance. Troop movements were calculated by predetermined tables for time and distance calculations based on units, drawn from FM 101-10, which were based on field and maneuver experience. Coordination between different echelons was done between the G3 through liaison officers. G3 also coordinated movement control through designated movement control offices, while traffic direction was done by army, corps, and division MP traffic control points.

Logistical traffic worked similarly. Supplies drawn from the beaches/ports moved by road or rail to designated depots under the control of the Communications Zone. Its was responsible for traffic control in the zone up to the rear army boundary, with traffic then routed to designated army depots for different classes of supply (generally divided into the various supply classes, although in practice the major tactical depots were Class I (rations), Class III (POL), and Class V (Munitions), other items were generally subsumed into general depots. Army maintained the supply points (depots), theoretically divisions drew from them using their own motor transport and were responsible for distribution to units, but often were augmented by army transportation...again, G3, working with G4, was responsible for coordinating supply movements with tactical movements. Coordination was actually the major role corps headquarters played in logistical operations...effectively the movement of supplies went directly from army to division. You can find more details on the depot and supply movements at:

http://usacac.army.mil/cac2/cgsc/carl/eto/eto-027.pdf