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

The next battle was Manassas (Second Bull Run), where the corps, still under command of General Porter, did some of the best fighting on that field, the largest regimental loss, in killed and wounded, in Pope's entire Army at that battle, occurring in the Duryee Zouaves, one of Porter's regiments. The two small divisions of Morell and Sykes sustained a loss there of 331 killed, 1,362 wounded, and 456 missing; a total of 2,151, out of about 6,500 engaged; Griffin's Brigade not being in action.

At Antietam, Porter's Corps was held in reserve; still, it was drawn on freely during the day, so that Sykes' Division was, almost wholly, in action. Soon after this battle a third division was assigned to the corps, taking the place of the Pennsylvania Reserves. This new division was commanded by General Humphreys, and was composed of two brigades; the regiments were all from Pennsylvania and were mostly nine-months men, newly recruited.

General Daniel Butterfield commanded the corps at Fredericksburg, and Generals Griffin, Sykes, and Humphreys the divisions; loss, 206 killed, 1,669 wounded, and 300 missing; total, 2,175. Over half of the loss fell on Humphreys' new recruits, who made a dashing attempt, under his personal leadership, to carry Marye's Heights after all other efforts had failed.

General Meade succeeded Butterfield, and led the corps to Chancellorsville, where it was but partially engaged; loss, 69 killed, 472 wounded, and 159 missing. The time of the nine-months regiments in Humphreys' Division expired soon after Chancellorsville, and that division was necessarily discontinued; but upon the news of Lee's invasion, in 1863, the Pennsylvania Reserves, who were then on duty in Washington, petitioned that they be allowed to march to the defence of their state. Accordingly, two brigades of the Reserves rejoined the Army of the Potomac, and were assigned to the Fifth Corps, in which they again served as the Third Division, this time under command of General S. W. Crawford.

General Meade having been promoted to the command of the Army, just before the battle of Gettysburg, General Sykes succeeded to his place; the divisions were commanded at Gettysburg by Generals Barnes, Ayres, and Crawford. The corps distinguished itself in that battle by its fighting in the wheat-field, and also by the gallant action of Vincent's Brigade in seizing Little Round Top, just in time to save the Army from what might have been a serious disaster. The corps' loss at Gettysburg was 365 killed, 1,611 wounded, and 211 missing; a total of 2,187, out of about 11,000 actually engaged.

The regular troops of the Army of the Potomac were all in the Fifth Corps, Second Division (Ayres' Division), and at Gettysburg these two brigades, under Colonels Day and Burbank, again displayed that marked efficiency which, at Gaines' Mill and on other fields, had made them famous, their thinned ranks becoming again sadly depleted under the terrible fire which they encountered.

General Sykes remained in command, and handled the corps on the Mine Run campaign; the division generals were Bartlett, Ayres, and Crawford.

In March, 1864, the First Corps was transferred to the Fifth, and General G. K. Warren was assigned to the command. The First and Second Divisions of the Fifth Corps were consolidated, forming the First Division, under General Griffin, while the Third Division--Crawford's Pennsylvania Reserves--remained unchanged; the First Corps had been consolidated into two divisions, prior to the transfer, which now became the Second and Fourth Divisions of the Fifth Corps, under command, respectively, of Generals Robinson and Wadsworth. Under this reorganization, the Fifth Corps contained 67 regiments of infantry, and 9 batteries of light artillery (48 guns), numbering in all 25,695 officers and men “present for duty, equipped.”

General Wadsworth was killed in the battle of the Wilderness, and General Robinson was severely wounded, losing a leg at Spotsylvania. General Cutler, of the Iron Brigade,