The Battle of Gettysburg is frequently referred to as the watershed campaign of the entire American Civil War.  In that encounter in 1863, the Confederate army proved to be the aggressive force, and to a large extent the Union strategy aimed simply to prevent Lee from achieving his own strategic aims.

Lee's strategic aims in the early summer of 1863 had been forged by two years of war into a single strategic vision. Paramount above all other war aims was the need to establish the Confederacy as a true and independent nation. The only method to allow this independence was through warfare, in forcing the United States to admit that the heretofore united country was now two separate nations. To accomplish this task with military means, Lee did not have to win the war, but could simply force a draw. The North did not have to lose the war to establish the Confederate nation, but to simply tire of the struggle and allow the South to form a new nation in peace.

In contrast, the harsh reality of the first two years of war brought home to Lee the fact that the South could only wage war for a limited period of time. The resources necessary for a protracted struggle were absent from the Confederate arsenal. Most serious of all the deficiencies faced by the Confederacy was a limited pool of manpower to fill her armies, which dwindled after every battle. Lee wrote in June 1863, "we should not therefore conceal from ourselves that our resources are constantly diminishing..." However, the military solution seemed to be the only way to achieve independence. By 1863, hope of foreign intervention was gone, and it was clear that for the South to forge a new nation, the only chance of success lay on the battlefield.

In truth, Lee already had won many battles, but always the Union armies came back into the field, frequently stronger than before. On 10 June 1863, Lee expressed his thoughts in a letter to President Jefferson Davis, stating, "Conceding to our enemies the superiority claimed by them in numbers, resources, and all the means and appliances for the carrying on of the war, we have no right to look for exemptions from the military consequences of a vigorous use of these advantages..." Without a change in the war, time and chance alone predicted an eventual defeat for the South.

Faced with fewer resources and a limited period of time in which to wage war, Lee chose an offensive strategy to achieve his nation's independence. In Lee's eyes the best hope of the South was targeting the will of the North to continue the war. The Southern general believed that after all the losses in two years of war, a Confederate army invading Northern soil and defeating a Union army once again perhaps might influence the growing peace movement in the Northern States, and the fall elections of 1863 would swing the North toward a negotiated peace. Lee wrote, "It seems that the most effectual mode of accomplishing this object, now within our reach, is to give all the encouragement we can consistent with the truth, to the rising peace party of the north..."

The road to Gettysburg now lay paved for the Lee and his army of Northern Virginia. In a dispatch written at Williamsport, Maryland on 25 June 1863 to President Davis, Lee states, "It seems to me that we cannot afford to keep our troops awaiting possible movements of the enemy, but that our true policy is, as far as we can, so to employ our own forces as to give occupation to his at points of our selection." Lee's strategic vision and the life or death of the Confederate nation would be determined at a small crossroads town in Pennsylvania on the first three days of July 1863.

The Battle of Gettysburg was fought July 1—3, 1863, in and around the town of Gettysburg, Pennsylvania. The battle with the largest number of casualties in the American Civil War^]it is often described as the war's turning point. Union Maj. Gen. George Gordon Meade's Army of the Potomac defeated attacks by Confederate Gen. Robert E. Lee's Army of Northern Virginia, ending Lee's invasion of the North.

After his success at Chancellorsville in Virginia in May 1863, Lee led his army through the Shenandoah Valley to begin his second invasion of the North—the Gettysburg Campaign. With his army in high spirits, Lee intended to shift the focus of the summer campaign from war-ravaged northern Virginia and hoped to influence Northern politicians to give up their prosecution of the war by penetrating as far as Harrisburg, Pennsylvania, or even Philadelphia. Prodded by President Abraham Lincoln, Maj. Gen. Joseph Hooker moved his army in pursuit, but was relieved just three days before the battle and replaced by Meade.

Elements of the two armies initially collided at Gettysburg on July 1, 1863, as Lee urgently concentrated his forces there, his objective being to engage the Union army and destroy it. Low ridges to the northwest of town were defended initially by a Union cavalry division under Brig. Gen. John Buford, and soon reinforced with two corps of Union infantry. However, two large Confederate corps assaulted them from the northwest and north, collapsing the hastily developed Union lines, sending the defenders retreating through the streets of town to the hills just to the south.

On the second day of battle, most of both armies had assembled. The Union line was laid out in a defensive formation resembling a fishhook. In the late afternoon of July 2, Lee launched a heavy assault on the Union left flank, and fierce fighting raged at Little Round Top, the Wheatfield, Devil's Den, and the Peach Orchard. On the Union right, demonstrations escalated into full-scale assaults on Culp's Hill and Cemetery Hill. All across the battlefield, despite significant losses, the Union defenders held their lines.

On the third day of battle, July 3, fighting resumed on Culp's Hill, and cavalry battles raged to the east and south, but the main event was a dramatic infantry assault by 12,500 Confederates against the center of the Union line on Cemetery Ridge. The Pickett-Pettigrew assault, more popularly known as, Pickett's Charge, momentarily pierced the Union line but was driven back with severe casualties. Stuart's cavalry attempted to gain the Union rear but was repulsed. 

Operational and tactical problems turned these three days of battle into a defeat of the Southern offensive strategy. Certain successes were achieved by Lee at both levels, to include transferring the seat of the war into the north for a season, and in bringing Union forces away from threatened points of the Confederacy such as the North Carolina coast.

On July 4, Lee began withdrawing his army toward Williamsport on the Potomac River.  His train of wounded stretched more than fourteen miles.  For a variety of reasons, the Union Army did not conduct an active pursuit.

However, after the battle, Lee wrote to his president, "No blame can be attached to the army for its failure to accomplish what was projected by me... I am alone to blame, in perhaps expecting too much of its prowess and valor....with the knowledge I then had and in the circumstances I was then placed, I do not know what better course I could have pursued..." Although the Civil War conflict would continue for two more years, the Battle of Gettysburg signaled the turning point for the Confederacy and its eventual defeat.

Later, in November of that year, President Lincoln travelled by train to Gettysburg and used the dedication ceremony for the Gettysburg National Cemetery to honor the fallen Union soldiers and redefine the purpose of the war in his historic Gettysburg Address.