internecion = mutual destruction (such as result of a nuclear war)

Not to be confused with:
iinternecine
adj.
5L internecinus < internecare, to kill, destroy < inter3, between + necare, to kill: see NECRO36
1 orig., full of slaughter or destruction
2 deadly or harmful to both sides of a group involved in a conflict, as a civil war; mutually destructive or harmful
3 of or involving conflict within a group