Despite the claim of victory at Gettysburg and a so-called high-water mark of the American Confederacy, the Northern army nearly twice General Robert E. Lee's strength was badly mauled and in no condition to contest Lee's return to Virginia. Lee's army did not re-cross the Potomac until 13 July and was not "seriously annoyed or molested in the interval" from a quiet 4 July. Lee immediately moved to the Rapidan river to confront the Northern army as it moved into Virginia east of the mountains.
Bernhard Thuersam, Chairman
North Carolina War Between the States Sesquicentennial Commission
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Lee Faces the Usual Odds at Gettysburg
"After the assault on the enemy's works on the 3rd of July, there was no serious fighting at Gettysburg. The 4th passed in comparative quiet. Neither army evinced any disposition to assail the other. Notwithstanding the brilliant achievements of [Generals Richard] Ewell and [A.P.] Hill on the first day, and the decided advantage gained by Longstreet on the second, the failure of the operations on the third day, involving as they did, but two divisions of the army, deprived us of the prestige of our previous successes, and gave a shadow of right to our adversary's claim of having gained a victory.
Their exultation, however, should be tempered with moderation, when we consider that, after one day of absolute quiet, the Confederates withdrew from their front without serious molestation, and with the bridges swept away, and an impassable river in rear, stood in an attitude of defiance until their line of defeat could be rendered practicable, after which they safely re-crossed into Virginia.
Then, again, so serious was the loss visited upon the Federals in the engagements of the first and second days, and so near success was the effort to storm their position on the third day, that they were themselves undecided as to whether they should stand or retreat.
In discussing several councils or conferences held by General Meade with his corps-commander, General Sickles testified, before the Committee on the Conduct of the War, that the reason the Confederates were not followed up was on account of differences of opinion whether or not the Federals should themselves retreat, as "it was by no means clear, in the judgment of the corps-commanders, or of the general in command, whether they had won or not."
On the 20th of July, 1863, after the return of General Lee to Virginia, his army numbered forty-one thousand three hundred eighty-eight effective, exclusive of the cavalry corps [of about 7600]. It appears . . . that General Lee's loss in the Pennsylvania campaign was about nineteen thousand.
Concerning the strength of the Federal army [in late June 1863] . . . General Hooker's . . . total effective (force of officers and men) [was] fully one hundred and twelve thousand . . . against the Army of Northern Virginia at sixty-two thousand of all arms – fifty thousand infantry, eight thousand cavalry, and four thousand artillery – and I believe these figures very nearly correct."
(Four Years With General Lee, Walter H. Taylor, Indiana University Press, 1962, pp. 110-113)