Bloody Arrow
From Halopedia, the Halo wiki
Bloody Arrow was a UNSC emergency code. Used during combat operations, the code signifies a complete route for UNSC forces, all friendly positions and forces have been overrun by enemy forces, and the combat operations are a decisive defeat.
The UNSC is forced to issue these constantly during conflicts with the Covenant during the Human-Covenant War. It was also declared after Sentinels overtook Onyx.
