internecine

Mutually destructive; most often applied to warfare.

Internecine strife in Gaza claimed its most senior victim yesterday when militants assassinated one of the most hated security chiefs there.

Characterized by struggle within a group, usually applied to an ethnic or familial relationship.

The Mongol people were plagued by internecine conflict until Genghis Khan unified them by focusing their aggression outwards on other peoples.

During the year of my engagement — 1869 — while I was out on the lecture platform, the daily letter that came for me generally brought me news from the front — by which expression I refer to the internecine war that was always going on in a friendly way between these two orthographists about the spelling of words.