The Lost Cause:
An interpretation of the American Civil War viewed by most historians as a myth that attempts to preserve the honour of the South by casting the Confederate defeat in the best possible light. It attributes the loss to the overwhelming Union advantage in manpower and resources, nostalgically celebrates an antebellum South of supposedly benevolent slave owners and contented enslaved people, and downplays or altogether ignores slavery as the cause of war.
Definition provided by Encyclopedia Britannica