In the context of the American Civil War (1861-1865), the border states were slave states that had not declared a secession from the United States. Four slave states never declared a secession: Delaware, Kentucky, Maryland, and Missouri. Four others did not declare secession until after the 1861 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 Confederate Virginia and became a new state in the Union.