The war fought between the forces of the Union and Confederacy was the American Civil War, which lasted from 1861 to 1865. It arose primarily from disputes over slavery and states’ rights, with Southern states seceding from the Union to form the Confederate States of America. The conflict was characterized by several major battles, deep societal divisions, and significant loss of life. It ultimately resulted in the preservation of the Union, the abolition of slavery, and the transformation of the American social and political landscape. The war left lasting implications for race relations and federal authority in the United States.