On September 25, 1861, Maj. Gen. G. W. Smith was assigned to the command of the II Corps, Army of the Potomac, which was organized to consist of all the troops not hitherto assigned to the I Corps. After October 2nd, the force was known as the 2nd Division and contained five brigades. It numbered almost 20,000 men, and passed into the Reserve, 2nd Division, and D. H. Hill's Division of the Army of Northern Virginia.
Most of these troops finally came under the command of Lt. Gen. Thomas J. "Stonewall" Jackson and became known as the II Corps of the Army of Northern Virginia, after the battle of Antietam.
After Jackson's death, Lt. Gen. R. S. Ewell succeeded to the corps, after it had been temporarily headed by Brig. Gen. J.E.B. Stuart and Maj. Gen. A. P. Hill.
On May 30, 1863, 2 divisions were detached to enter the III Army Corps. The corps was commanded by Lt. Gen. Jubal A. Early in the Shenandoah campaign of 1864, and in the closing months of the war around Petersburg, by Lt. Gen. John B. Gordon.