The Battle of Shiloh started by a surprise attack led by confederate general Albert Sidney Johnson against Union general Ulysses S. Grant and his army
This battle was considered one of the bloodiest battles of the war. At first the Confederate Army had the battle in their hand.
The Confederate Army had a bigger advantage with land. Tennessee. They were more familiar with the land.
The Confederate attack stalled and the Union was able to push them out and win the battle. The battle ended on April 7th.
The win for the Union allowed them to control nearly all of Western Tennessee including a major rail center. The Confederate Army also lost one of their greatest generals in that war.