What was the importance of the Battle of Gettysburg?

At the start of the Gettysburg Campaign both armies were separated by the Rappahannock River in Virginia. The North had attacked across the river twice, in the Battle of Fredericksburg (December 1862) and the Battle of Chancellorsville (May 1863). Both were Confederate victories, although both times the North was able to withdraw back across the river and safely rebuild.

Lee knew he could not just sit south of the river and throw back Northern attacks. His army could not replace its casualties while the North could, meaning he would grow ever weaker in comparison. Remaining in one location had stripped the nearby area of food, forage and firewood, and the Southern rail system could not supply his army properly. Already he had had to disperse his hungry artillery horses away from the army to keep them alive, limiting his mobility in an emergency. And Lee knew that some day the North might find the winning combination.

Lee’s plan was to take the war to the north in a move up the Shenandoah Valley. This would let the farmers there harvest their crops for the Confederacy, while Lee’s army could forage in the rich and untouched lands of Pennsylvania. It would threaten Union cities such as Baltimore, Harrisburg and Philadelphia. And it would give Lee a chance to fight and win a battle in the open, where he could finally pursue and possibly destroy the beaten enemy. Lee saw it as the best way to end the war before the South was trapped in an unwinnable battle of attrition.

Lee maintained the initiative all through the battle, launching major attacks each day. But by the evening on July 3rd he had reached the end of his strength. His army had lost heavy casualties and he was critically low on ammunition, particularly artillery. He was well into Union territory where reinforcements would not be available, while Meade’s force was rapidly growing. He pulled back into a strong defensive line on the 4th, hoping Meade would attack and spend himself the way Lee had for three days, but Meade refused to rise to the bait. Lee’s only choice was to return to Virginia.

The Battle of Gettysburg is considered a turning point. Although it did not involve the largest number of troops the battle had the highest casualties of any battle of the Civil War. Up until then Lee might have been able to win the war with a stunning victory that forced the North to concede defeat. Afterwards the best he could hope for was to make the North’s victory so costly they would give up in exhaustion. Lee’s heavy losses in men and particularly officers would be a problem for the rest of the war. And for the rest of the war Lee was on the strategic defensive, forced into the war of attrition he feared, and eventually cornered in an unwinnable siege around Richmond.