The Battle of Antietam was the deadliest single-day battle in the Civil War, changing the course of the conflict.
Battle of Antietam: This battle, occurring in September 1862, became the deadliest single-day battle in the Civil War, with over 23,000 casualties, leading to Lincoln issuing the Emancipation Proclamation.
First Battle of Bull Run: It showed the Union it would not easily defeat the Confederacy, ruining Northern morale and changing perceptions about the war's duration.
Peninsula Campaign: Impressed President Lincoln with Ulysses S. Grant's leadership, causing Lincoln to lose confidence in General George McClellan.
https://brainly.com/question/34611298