Lee was never one to confide all his feelings or beliefs to one sheet of paper, but it seems likely that he decided by the first of June. He was under pressure from many leaders of the Confederacy to do something to relieve the pressure on Vicksburg. Some, including General Longstreet, believed that Lee would do best to go west himself and do the job that Joseph Johnston seemed incapable of. Lee did not think this was the right course of action: he wanted to be with the men who trusted him so well and vice versa.

In a series of letters to Jefferson Davis, Lee indicated his desire to cross the Potomac and bring the war to the enemy. The North had, in his mind, tasted very little of the war so far, and it would please his men to live off the fat of Northern land. What Lee did not say explicitly, but what Jefferson Davis understood all too well, was that the Army of Northern Virginia could not safely remain where it was. Even in the aftermath of its glorious victory at Chancellorsville, the army was on the verge of starvation. The lands around the Rapidan and the Rappahannock had been foraged by both armies for so long that they simply could not support the presence of sixty to seventy thousand armed men.