Its brilliant record is closely interwoven with the history of the Virginia campaigns of 1862–1863, in which it fought during two eventful years.

But this aggregate was maintained only briefly, as Porter's Division was taken away soon after to form part of the newly organized V Corps.

Upon the evacuation of Yorktown, the III Corps led the pursuit of the retreating enemy, attacking them at Williamsburg on May 5, with Hooker's and Kearny's Divisions.

At Fair Oaks, its next battle, 209 were killed, 945 wounded, and 91 missing, principally Charles D. Jameson's and Hiram G. Berry's Brigades of Kearny's Division.

It arrived at Warrenton Junction on August 26, and on the following day the Excelsior Brigade had a sharp fight at Bristoe Station.

Cuvier Grover's Brigade, of Hooker's Division, fought desperately at the railroad embankment, in which the use of bayonets and clubbed muskets was officially reported.

After Second Bull Run, the III Corps was severely understrength and so during the Maryland Campaign in September, it was left behind in Washington DC to rest and refit.

The corps was not prominently engaged at Fredericksburg, although under a heavy fire; still, its casualties amounted to 145 killed, 837 wounded, and 202 missing; total 1,184, over half of which occurred in J.H.

The depleted ranks were still further lessened by the loss of four New York regiments whose two years term of enlistment had expired; in addition, the division of nine month troops had gone home.

Sickles wanted to occupy the slightly higher ground there, but the corps was forced to defend a salient that was too long for its size.

On July 14, the battered III Corps was strengthened by the addition of Maj. Gen William H. French's Harper's Ferry garrison.

Another minor affair occurred at Kelly's Ford, Virginia, November 7, 1863, in which some regiments of Birney's (1st) Division were under fire.