The first was Richard S. Ewell. In many ways he was a natural choice, as he had served as Jackson's right hand in his famous Shenandoah Valley campaign. He had been absent from the army for months from a wound incurred in the Second Battle of Manassas.
The other was A. P. Hill, commander of what he called the Light Division. He was a very competent division commander, and was instrumental in some of Lee's great victories. His fault was that he was very quarrelsome. He had been in Longstreet's first corps until he quarreled with his commander. He was transferred to Jackson's second, but argued with him as well.
In the end, Lee decided to chose both of these men. He would reorganize the army into three corps. This would allow him to promote both men, and give the army more flexibility. Ewell would have the second corps, and one of his four divisions was given to Hill's new third corps. Hill also received one of Longstreet's divisions, and a new division of reinforcements. The army was composed of three corps of three divisions each, along with another division of cavalry.
This reorganization was a dangerous thing to do just before a major campaign – the invasion of the North. Ewell and Hill had fought well as division commanders, but no one knew how they would perform when advanced to the next level of command. But Jackson was no longer available, so it was a risk that had to be taken.