The Battle of Devil's Backbone, also known as the Action at Devil’s Backbone, was a military engagement in the Trans-Mississippi Theater of the American Civil War. Devil's Backbone is a ridge in the Ouachita Mountains approximately 4 miles (6.4 km) southwest of Greenwood, Arkansas. The battle was fought on September 1, 1863, in Sebastian County, Arkansas. The Union victory ensured the safety of the Fort Smith garrison until the end of the war.