The troops comprising the Second Corps originate known as the Second Corps of the Army of the Potomac, under the command of Major General Gustavus W. Smith. This unit was also known as the Second Division and was eventually subsumed into general Robert E. Lee's Army of Northern Virginia as a reserve in Maj. Gen. D. H. Hill's Division. When Lee was able to reorganize his army after finishing battles with Union Maj. Gen. George B. McClellan on the peninsula, he created this corps under the command of Lieutenant General Jackson, along with a sister corps under Lt. Gen. James Longstreet. Lee's reorganization was based on his evaluation of the performance of his division commanders during the Seven Days Campaign.