Answer:
The Battle of Shiloh in April 1862
Step-by-step explanation:
The battle in Shiloh in April 6-7, 1862, is considered as the biggest hinderance to Union's victory, as the battle was the bloodiest of the Civil War, with a total casualties for both Union and Confederates sides numbered over 20,000. This battle ended without any clear winner.
However, some considered Union to have won by a narrow victory, after the battle of Shiloh, Union troops laid siege to Corinth, forcing Confederate troops to withdraw Memphis Tennessee, which eventually fell to Union forces on June 6 1862.