William F. Fox, Lt. Col. U. S. V., Regimental Losses in the American Civil War, 1861-1865: A Treatise on the extent and nature of the mortuary losses in the Union regiments, with full and exhaustive statistics compiled from the official records on file in the state military bureaus and at Washington

Upon the opening of the campaign against Vicksburg, May 1, 1863, the Thirteenth Corps was composed of the four divisions of Osterhaus, A. J. Smith, Hovey, and Carr; these were also known, respectively, as the Ninth, Tenth, Twelfth, and Fourteenth Divisions, having been numbered thus while in the Army of the Tennessee. The corps, as thus composed, contained 40 regiments of infantry, 11 batteries of light artillery, and 6 companies of cavalry; numbering in all 32,648, present and absent, with 18,245 present for duty. To this should be added Ross's (13th) Division, stationed in Arkansas, which also belonged to the Thirteenth Corps, but which did not take part in the Vicksburg campaign. This division fought the battle of Helena, Ark, July 4, 1863.

The battle of Port Gibson, May 1, 1863, was fought almost entirely by the Thirteenth Corps, its losses in that action aggregating 125 killed, 678 wounded, and 23 missing; total, 826. The battle of Champion's Hill was fought by the Thirteenth and Seventeenth Corps, the former losing 231 killed, 987 wounded, and 145 missing; total, 1,363. The fighting at the Big Black River Bridge was a brilliant affair, in which the Thirteenth Corps alone participated; loss, 39 killed, 237 wounded, and 3 missing; total, 279, the bulk of which occurred in Lawler's Brigade of Carr's Division. In the first assault on Vicksburg, May 19th, the corps sustained a slight loss only; but in the grand assault of May 22d it suffered severely, losing 202 killed, 1,004 wounded, and 69 missing; total, 1,275. During the first twenty-two days of the Vicksburg campaign, the corps lost 3,393 men in action, which was supplemented during the siege by heavy losses in the trenches.

General McClernand was relieved from command on June 19th, by order of General Grant, and General E. O. Ord was appointed in his place. Grant was displeased with the tone and character of a congratulatory order issued by McClernand to his troops, and as McClernand declined to amend it he was relieved. After the capitulation of Vicksburg the Thirteenth Corps, under General Ord, moved with the Army to Jackson, Miss., and assisted in the investment of that place. Carr's Division at this time was commanded by General William P. Benton. In the operations about Jackson the corps lost 85 killed, 501 wounded, and 165 missing; total, 751. This includes the loss in Lauman's Division, of the Sixteenth Corps, which was temporarily attached to the Thirteenth.

Upon the evacuation of Jackson and retreat of the enemy, the corps returned to Vicksburg, and in the following month, (August, 1863) moved on transports down the Mississippi to New Orleans. The troops were assigned to duty at various places in the Department of the Gulf,--in Texas and Louisiana. General Osterhaus was succeeded in command of his division by General C. C. Washburn. The Third and Fourth Divisions fought at Grand Coteau, La., November 3, 1863. The winter of 1863-4 was spent in the vicinity of New Orleans and the Lower Mississippi, a part of the corps being stationed in Texas. Corps headquarters were in Texas, but were moved to Alexandria, La., on the 18th of April, as the Third and Fourth Divisions had accompanied Banks on his Red River Expedition of April, 1864. General McClernand was again in command of the corps; the Third Division was commanded by General Cameron, and the Fourth, by General Landram. The First and Second Divisions remained in Texas during the Red River Expedition, excepting Lawler's (2d) Brigade, of the First Division, which joined Banks' Army about the 20th of April. The Third and Fourth Divisions of the Thirteenth Corps were actively engaged at the battle of Sabine Cross Roads, La., April 8, 1864, in which they sustained considerable loss. They were also engaged at Cane River, and at Cloutiersville, La.

The corps organization was discontinued, June 11, 1864, and the troops transferred to other commands. It was reorganized, Feb. 18, 165, and Major-General Gordon Granger, of Chickamauga fame, was placed in command; the divisions were commanded by Generals