How was the battle of Shiloh devastating to both sides

Also known as the Battle of Pittsburg Landing, the Battle of Shiloh took place from April 6 to April 7, 1862, and was one of the major early engagements of the American Civil War (1861-65). The battle began when the Confederates launched a surprise attack on Union forces under General Ulysses S. Grant (1822-85) in southwestern Tennessee. After initial successes, the Confederates wereunable to hold their positions and were forced back, resulting in a Union victory. Both sides suffered heavy losses, with more than 23,000 total casualties, and the level of violence shocked North and South alike.