Information on this event are found in Dee Brown's "The Galvanized Yankees," U of Nebraska Press, 1963, Chapter 12, "A Note on the Galvanized Confederates," pp. 124-126.

The discussion sources the following from the Official Records:

HEADQUARTERS MILITARY STATION,
Alton, Ill., January 24, 1865.

Brig. Gen. H. W. WESSELLS,
Commissary-General of Prisoners, Washington, D.C.:

GENERAL: I have the honor to transmit herewith a special roll of prisoners belonging to various regiments in the service of the United States who enlisted in the Tenth Tennessee (rebel) Regiment(+) while held by the rebel authorities as prisoners of war at Andersonville, Ga.. and were captured by the U.S. forces at Egypt Station, Miss., in General Grierson's late expedition. These men were received here with other prisoners of war on January 17, 1865, and were duly reported as such, but special rolls corresponding with the accompanying were received at the same time from the authorities sending the prisoners The remarks on the rolls and the accompanying letter of Colonel Noble Third Iowa Cavalry, will explain the status and history of these men as far as known at these headquarters.

I am, general, very respectfully, your obedient servant,

ROY STONE,
Brevet Brigadier-General, Comdg. Military Prison and Post.

[Inclosure No. 1.]

STEAMER E. H. FAIRCHILD,
En Route for Cairo, Ill., January 13, 1865.

Lieut. JOHN S. LYTLE,
Eighth Iowa Infantry Volunteers,
In Charge of Rebel Prisoners of War on Board:

SIR: At the request of Capt. Samuel Wilson, provost-marshal, post Memphis, Tenn., communicated to me by yourself, I have to make the following statement touching the prisoners of war now in your custody and whose names are set forth on the roll to which this paper is attached: These men were captured by the First Brigade of Brigadier-General Grierson's troops, under command of Colonel Kargé, Second New Jersey Cavalry, at Egypt Station (Mobile and Ohio Railroad), on the morning of the 28th of December, 1864, with several hundred more prisoners belonging to the rebel army, under the command of Lieutenant-Colonel Burke, of the rebel service, and have, as they claim, been formerly in the service of the United States in the various regiments designated opposite their names on the roll. On the evening previous to the engagement at Egypt several of these men designated on the rolls deserted the rebels and, coming into our lines, gave information of the force opposed to us and reported that many of these men would not resist us in battle. In the engagement which ensued in the morning this proved true in many instances, although the fight was a severe one and required great valor on the part of Colonel Kargé's cavalry to gain the victory. The general report of these men to me during the time they were under my charge from Vicksburg to Memphis agrees in the following particulars: That they were prisoners of war at Andersonville, Ga., when they enlisted in the Confederate service; that at the time they were in great want of food, fuel, and clothing, which, with exposure to weather, rendered disease and death imminent to them all, and that many dead were carried from among the prisoners daily; that they were told there would be no exchange of prisoners, and if they would enlist in the Confederate service they would be received, taken from prison and treated like other Confederate troops; that these (on the rolls) were enlisted by Lieutenant-Colonel Burke, now a prisoner on board, and have been under his command since; that they were enlisted under an oath they do not now remember and many of them claim with the design and determination on their part to rejoin our ranks at the first opportunity, and that they did avail themselves of the only opportunity that had presented itself; that they were never fully trusted by the Confederates, being deprived of many privileges extended to other troops, kept under strict camp guard and unarmed; that they were given muskets on the day before the affair in which they were captured, and ammunition; but on the night before that foreigners were first solicited, but many others finally taken, and that they now wish to be sent to their old regiments to fight for the Union. These statements will not apply universally but generally to this class of prisoners.
My regiment was not in the engagement when these men were captured, nor do I know of my own knowledge their acts before and in the fight, but state that in this particular--which was communicated to me by officers on the march, this communication being given on the request before mentioned and to form the foundation for further inquiry by the authorities of the Government if' deemed important---from my intercourse with these men, I believe that most of them are worthy of clemency, a few of special favor, but many at the same time are not to be trusted. As to the more general effect of the treatment of these men upon other prisoners in the rebel prisons, and again upon the rebel Government, I am not called upon to express, and Brigadier-General Grierson (now under orders to report to Louisville, Ky.), Colonel Kargé, Second New Jersey Cavalry, at Memphis, Tenn., and Capt. S. L. Woodward, assistant adjutant-general on General Grierson's staff, can give more definite information in reference to the peculiar status of these men and the acts of particular individuals than is within my knowledge.

Very respectfully, yours,

JOHN W. NOBLE,
Colonel Third Iowa Cavalry.

[Inclosure No. 2.]

Extracts from reports of officers commanding troops in the expedition which resulted in the skirmish at Egypt Station, Miss., December 28, 1864, with reference to the capture by the Union forces of certain men who had enlisted in the Confederate Army while prisoners of war in rebel prisons.
Brig. Gen. B. H. Grierson, commanding Cavalry Division, Department of the Mississippi, and the expeditions, reports the capture of 500 prisoners at Egypt Station, adding "* * * over 100 of the prisoners captured at Egypt formerly belonged to our army, and were recruited from Southern prisons into the rebel service, and most of whom, I believe, were induced to join their ranks from a desire to escape a loathsome confinement. I commend them to the leniency of the Government * * *."

Col. Joseph Kargé, Second New Jersey Cavalry, commanding First Brigade, Cavalry Division, Department of the Mississippi, whose command was the principal force engaged, merely reports the capture of 500 prisoners, making no mention of their character. The Second Brigade, Cavalry Division, Department of the Mississippi, was not engaged at Egypt Station.

Col. E. D. Osband, Third U.S. Cavalry (colored), commanding Third Brigade, Cavalry Division, Department of the Mississippi, makes no mention of the character of the prisoners taken by his command.