The significant battle of the American Civil War that marked the transition towards Union victory is the Battle of Gettysburg, fought from July 1 to July 3, 1863. This pivotal confrontation is often considered the turning point of the war, as it halted General Robert E. Lee's second invasion of the North. The Union's victory at Gettysburg, coupled with the significant casualties suffered by the Confederate army, shifted the momentum in favor of the Union. The battle also rallied northern morale and strengthened support for the war effort, ultimately leading to the Union's triumph in 1865.