The Union Army was the land force that fought for the northern states during the American Civil War (1861-1865). Its primary goal was to preserve the United States and prevent the secession of the southern states, which formed the Confederate States of America. The Union Army was composed of volunteers and conscripts and was known for its larger size and resources compared to the Confederate Army. Key figures in the Union Army included generals like Ulysses S. Grant and William Tecumseh Sherman, who played crucial roles in leading campaigns against the Confederacy. The Union Army's victories at battles such as Gettysburg and Antietam were significant in turning the tide of the war, ultimately leading to the defeat of the Confederacy and the preservation of the Union.