INTERNECINE
internecine
(adjective) characterized by bloodshed and carnage for both sides; “internecine war”
internecine
(adjective) (of conflict) within a group or organization; “an internecine feud among proxy holders”
Source: WordNet® 3.1
Etymology
Adjective
internecine (not comparable)
Mutually destructive; most often applied to warfare.
Characterized by struggle within a group, usually applied to an ethnic or familial relationship.
Source: Wiktionary
In`ter*ne"cine, a. Etym: [L. internecinus deadly, murderous, fr.
internecare to kill, to slaughter; inter between + necare to kill;
akin to Gr. Necromancy.]
Definition: Involving, or accompanied by, mutual slaughter; mutually
destructive.
Internecine quarrels, horrible tumults, stain the streets with blood.
Motley.
Source: Webster’s Unabridged Dictionary 1913 Edition