Just an opinion , but I think Shaver was a Hindman guy, and when Holmes came and Hindman left, he was without a sponsor.
At one time or another, looks like he commanded some 3 or 4 Brigades.
Building on what Bryan posted, here is a timeline for Shaver:
Excerpted from my personal papers
All dates are 1862 except where noted
Entries are from The Peter Wellington Alexander papers unless otherwise noted
4/12 Hdqrs First brigade, Hindman’s Div, 3rd army corps, army of the Mississippi- Report of Col. R. G. Shaver, Seventh Arkansas Infantry, commanding First Brigade
Official Records, Series 1 - Volume 10 (Part I)
5/2/62 Corinth-Rec’d of ordnance officer at Corinth, M Levy Acting Ord. officer 1st Bgde-Col R G Shaver
Shaver’s compiled service records
7/12 Hindman’s AG Newton to Shaver, cdg-You have been assigned to the command of the brigade to be composed of the forces mentioned in the order enclosed herewith - You will have command of all detached forces, whether cavalry or infantry, now at or near Pine Bluff , or ordered there. - You will scout with your Cavalry actively towards Clarendon and other points below on White River, and along the Cut Off, opposing any movement of the enemy, and giving information promptly from time to time, to these Head Quarters - If practicable, you will establish a Cavalry camp, at or near Arkansas Post
Head Quarters Army of the South West Little Rock July 12th Special Orders No 31
I-Col Shaver is hereby assigned to command of the brigade to be composed of Col Grinstead's Regt, Dawson's Ark Regt and an additional regiment to be composed of the companies under command of Col [Thomas M.] Whittington, the surplus Companies with Col Dawson, and other companies in Col Grinstead's and Gen Roane's district. - He will establish a - camp of instruction at, or sufficiently convenient to, Pine Bluff , collect his infantry and artillery, and immediately enter upon a rigorous course of instruction, reporting directly to these Head Quarters, until Gen Roane shall have moved to that vicinity, and thereafter to him.
7/24 Little Rock, Newton A.A. Gen to Gen. Roane, Pine Bluff, Assume command of the forces at and near Pine Bluff, and in front of it. Put Shaver in command of the camp of instruction until one of the new Regiments is formed, and put him in command of that - Did any of your troops came with you?
7/26 Date of rank
Shaver’s compiled service records
8/2 Head Quarters Army of the South West, Little Rock, Special Orders No. 54
VIII Brig Gen John S. Roane is assigned to the command of the troops, at Camp White Sulphur Springs, Arkansas], and will establish his Head Quarters there.
IX The following arrangement of the troops at Camp White Sulphur is announced: -
First Brigade Col R. G. Shaver Cdg –
1 Dawson’s' Regiment Arkansas Infantry
2 Grinstead’s [Regiment Arkansas Infantry]
3 Portlock's Hart's Battery [Arkansas Infantry]
…
…
8/9 Head Quarters Army of the South West, Little Rock, Special Orders No 61
VI Brig Gen John S. Roane is relieved of duty till further orders.
VIII Col R. [Robert] G. Shaver is placed in command of the troops at Camp White Sulphur, until the arrival of Col Robert R. Garland, when the latter will assume command of the forces there, and organize the same temporarily as a division, of one brigade of which, he will retain the immediate command, and Col Shaver the command of the other
8/14 Head Quarters Army of the Southwest, Little Rock, Special Order No 66
I-Capt W.B. Denson's Cavalry Company is hereby accepted as Cavalry, and will be reported at once to Col Shaver Cdg at Pine Bluff, , with whom it will remain until further orders.
8/15 To Col R. [Robert] G. Shaver Pine Bluff: The "Sapper & Miners" are to be made up solely from your brigade. RC Newton AA Gen
8/16 Head Quarters Army of the South West, Little Rock, Special Orders No 68
II. So much of Paragraph VIII. Special Orders No 61, of this series, directing Col. R. R. Garland to "assume command of the forces at Camp White Sulphur upon his arrival there" is hereby revoked, Col R. G. Shaver, now in command being the ranking officer will retain command at that place.
8/25 Camp White Sulphur Springs-to Col R W Johnson-The undersigned field officers of the 3 Regts now constituting a Bgde of Ark Infy under the command of Col Shaver seek your influence to have him promoted to BGen. He commanded a Bgde at Shiloh gallantly. We regard him as an efficient & meritorious officer…
Grinstead’s Regt Ark
Col Grinstead
Lt Col McMillan
Maj Crenshaw
Dawson’s Regt 19th Ark
Col Dawson
Lt Col Hutchins
Maj Hamiter
Portlock’s Regt Ark Infy
Lt Col Whittington
9/22 Hindman to Shaver, Pine Bluff-From information I have received I deem it advisable that you should accept immediately by telegraph the offer made you by Gen Holmes.
Various dates of appointment as Colonel of 38th Arkansas in Shaver’s compiled service records:
9/21The 38th Arkansas Regiment was inducted into CSA at Jacksonport, Ark.
9/24 Shaver was appointed this date as Col of the 38th
9/24 Appointed by Holmes
9/24 Appointed by Hindman
9/24 the 38th Ark field officers announced
9/25 Newton to Shaver at Pine Bluff-Gen Hindman will leave here Tues. He has requested that you be relieved at Pine Bluff at once
9/25 Holmes’ order-Lt Col Anderson is hereby announced as AG to the dept & chief of staff. He will immediately relieve Col Deshler in the duties of that office. The latter upon being relieved will proceed to White Sulphur & relieve Col Shaver in command of the Bgde now there. Col Shaver will then report for duty with his Regt at Pocahontas.
9/28 S O #39-
VI-Col Shaver is relieved of command of Shaver's Bgde, Roane Div, & will assume command of his Regt at Pocahontas..
9/28 Hqs to Col H. L. Grinstead Pine Bluff-You will move via Prattville where you will receive orders from Col Shaver
9/29 Hindman to Gen McBride, Pocahontas-your Infy is ordered to Yellville to report to Gen Parsons and cavalry and arty to Thomasville, Mo to report to Burbridge as previously ordered
If you decide on leave of absence until your resignation is acted on, Col Shaver will assume your command executing the above orders.
10/11 Col Shaver broke camp, and the Bgde headed westward arriving Yellville on Oct 22.
Embattled Arkansas: The Prairie Grove Campaign of 1862. Author, Michael E. Banasik
10/22 Shaver arrives at Yellville-Parson's and Shaver's Bgdes.... had united at Yellville before marching south to Hindman’s camp. Col Shaver broke camp on 10/11 and moved west to Smithville on 10/13. On 10/15, he reached Evening Shade and after 11 days finally reported to Parsons at Yellville 10/22. Parsons was expecting 4000 Infy with Shaver, but he had only 3000 including 1000 unarmed and all destitute of supplies and equipment.
Embattled Arkansas: The Prairie Grove Campaign of 1862
10/26 Hindman cancelled the Forsyth operation [a joint operation with Shaver and Parsons that Hindman had ordered from Little Rock before he returned to the North West] and now directed Parsons to join him.
Parsons' command moved west and arrived at Bellefonte 10/30; then to Carrollton and bypassed Huntsville and reached Kingston 11/2; then crossed the Boston Mountains the hardest part of the march. Then rested for a day waiting on broken down wagons to rejoin then last leg on to Hindman's camps arriving on Mulberry River 11/7
Embattled Arkansas: The Prairie Grove Campaign of 1862
10/30 arrive Bellefonte -our Bgde still under Shaver-now leaving N Central, Ark, causing desertions... plus we don’t like Shaler-meet Monroe/Fagan’s Ark cavalry
The Turnbo Manuscripts by Silas Claiborne Turnbo
11/9 S O #38* Hqs Dist of Ark-camp on Mulberry-announcing organization of 1st Corps Trans Miss Army
Third Division-Parsons
1st Bgde-Col Stein cdg
1 Steins Regt Missouri Infy
2 Hunter “
3 Caldwell “
4 White “
Tilden Missouri Btry
2nd Bgde-Col Shaver
Shaver Regt Arkansas Infy
Shaler “
Grinstead “
Adams “
Roberts Missouri Btry
*Called S O #39 in Embattled Arkansas: The Prairie Grove Campaign of 1862
12/12 Organization of the Army of the Trans-Miss Department, Lt. Gen. Holmes, C. S. Army, commanding
Third Division-Parsons
Second Brigade-Col. R. G. Shaver
___Arkansas, Col. C. W. Adams
27th Arkansas, Col. James R. Shaler
33d Arkansas, Col. H. L. Grinsted
38th Arkansas, Col. R. G. Shaver
Roberts (Missouri) battery
Official Records-Series 1 - Volume 22 (Part I)
1/16/63 Hqs, 1st Corps T-M Army Little Rock-Hindman to Col S Anderson-The information called for by note of this date, is furnished as follows:
…
2d Div, Brig Gen Fagan
3rd Bgde, Col Shaver
1 Shaver's Regt Ark Infy
2 Grinstead’s “
3 Shaler's ‘
4/1/63 Price assumes command of the Div
4/2/63 Little Rock, Gen Price to Bgde cdrs: Fagan, McRae, Parsons & Tappan-By instructions from Dist Hqs the Bgdes of this Div will be prepared to move from here to Cunningham’s Lake about 6 miles W of Little Rock
Shaver reports:
-I transferred to TM & was assigned command of a Bgde by Gen Hindman & led it until Sept 62, when the question of the legality of my position was raised.
-Gen Holmes reduced me from the command of a Bgde to the command of a Regt I now command.
-I was then ordered to relieve Gen McBride of the command of his Bgde & led it until replaced by the appointment of Gen Tappan. Have since been in command of my Regt except for time on recruiting duty
[Searching my files for source]
10/1 Tappan appointed volunteer aid by Gen Holmes
11/5 Tappan appointed Brig Gen by General Holmes
Fold 3 Tappan CSR