Final answer:
The Battle of Gettysburg marked a turning point in the Civil War because it greatly weakened Lee's army, shifted momentum in favor of the Union, and because Confederate forces never attempted another invasion of the North after their severe losses.
Step-by-step explanation:
The Battle of Gettysburg is considered a key turning point in the American Civil War primarily because it greatly weakened Lee’s army. The battle, which took place from July 1-3, 1863, resulted in the largest number of casualties in the civil war and marked the last time Confederate General Robert E. Lee would attempt to invade the North. The Union's defense and eventual victory at Gettysburg, along with their success at Vicksburg, were crucial in shifting the momentum of the war in favor of the Union.
During the pivotal third day of Battle at Gettysburg, Confederate forces, under the command of General Lee, launched Pickett's Charge against the Union defenses on Cemetery Ridge, resulting in devastating losses for the Confederates. The battle not only inflicted significant casualties upon the Confederate Army—amounting to over a third of Lee’s forces—but also subsequently dampened the Confederacy's hopes of gaining support from Europe. Thus, while Gettysburg did not win the war outright for the Union, it marked a psychological and strategic blow to the South, from which they never fully recovered.
This confrontation did not make Europe a Union ally, nor was it the first battle the Confederacy lost; however, the concurrent Union victory at Vicksburg and defeat of Lee's forces at Gettysburg did turn the tide against the Confederacy, leading to its eventual surrender in 1865.