A 21st-century conflict in the United States which, according to Captain Pike, was the first step on the road that led Earth through the Eugenics War to World War III.
The Second Civil War is named by Christopher Pike in the first episode of Strange New Worlds, also titled Strange New Worlds, as the opening stage of the chain of conflicts that almost destroyed humanity in the 21st century.
Speaking to the divided factions of Kiley 279, Pike shows them archive images of unrest on Earth and explains that a fight over competing ideas of liberty grew into the Second Civil War, then the Eugenics War and finally World War III, in which some thirty per cent of the population died.
Pike uses the story as a warning: the people of Kiley 279 have built a warp bomb and stand where Earth once stood. Nothing more is said on screen about the course of the war itself.