Alternate History

From The Writerium - the wiki for writers

A genre in which the author explores what might have happened if historical events had happened differently. What if X had become president instead of Y? What if A had failed his mission to deliver vital information to B? What if disaster struck the newly-forming government of X? What if X had been a soldier instead of a politician?

While it may offer more room for creativity than Historical Fiction, research into the place and period one is writing about is still a necessity.