In the context of the American Civil War, the border states were slave states that did not secede from the Union (the ones that did so later joined the Confederacy). Four slave states never declared a secession: Delaware, Kentucky, Maryland, and Missouri. Four others did not declare secession until after the Battle of Fort Sumter: Arkansas, North Carolina, Tennessee, and Virginia—after which, they were less frequently called "border states". Also included as a border state during the war is West Virginia, which broke away from Virginia and became a new state in the Union in 1863.