The Battle of Gettysburg turned the tide of the American Civil War because the Union won the battle, thus forcing the Confederate army to retreat from Union territory. The Confederates lost a large number of soldiers and were never able to fully recover, resulting in their ultimate defeat.
The Battle of Gettysburg took place from July 1 to July 3, 1863, two years into the Civil War. The Confederate army started the Battle of Gettysburg by invading Union territory in central Pennsylvania. Confederate Army General Robert E. Lee hoped to score a major victory on Northern soil to cripple the Union Army and also persuade Great Britain and France to come to the Confederate Army's aid.
The battle commenced on July 1 when General Lee sent a division of Confederate troops to invade Gettysburg. Several brigades of Union troops met them. Fighting began shortly after, with reinforcements from both sides arriving by the end of the day. After nearly three days of intense fighting, the 85,000-strong Union troops proved too strong for the 75,000-Confederate troops on the battlefield, and Lee retreated from Gettysburg with his remaining troops on July 4.
Although both sides lost a massive number of troops that day, the Confederate army lost nearly a third of its entire army, which it was never able to regain. The crippling loss, combined with a defeat in Vicksburg, Mississippi, also on July 4, is why many historians view the battle as the major turning point of the Civil War. It was also the largest battle of the war, as well as the largest ever fought in North America.