The battle of Antietam was the bloodiest battle in the civil war.
The Battle of Bull run was a union attempt to end the civil war quickly. The union wanted to launch a surprise attack on the Confederate capital in Richmond which was 25 miles from Washington D.C. The new union army (which was full of recruits) was massacred by a strong 30,000 troop Confederate army.
The battle of Shiloh was a harsh battle for both sides. The Confederate army decided a surprise attack on the union and drove them out. After being chased by the Confederates, the Union general Grant told his commander to hold a critical point in the battle. This was nicknamed the hornets' nest.