Answer :
Answer: The Battle of Gettysburg
Explanation:
This battle, which lasted from July 1-July 3, 1863, was a huge victory for the Union army. The Army of the Potomac defeated General Robert E. Lee at Gettysburg, Pennsylvania. the Confederate army was forced into a full retreat, which bolstered the Union army's morale. Lee's forces were considered "Invincible", following their victory at the Battle of Chancellorsville. The Battle of Gettysburg was a turning point because the Union army whipped the Confederate forces, and sent them running to Vicksburg, Mississippi, which would fall on July 4, 1863. These two victories sent a surge of energy into the Union army, and they were rendered "Unstoppable".