From Halopedia, the Halo wiki
Branch:
UNSC Marine Corps
Type:
Infantry division
Role:
Locate close with and destroy the enemy by fire and maneuver and repel the enemy's assault by fire and close combat
Size:
15,000+
The 21st Marine Division was a UNSC Marine Corps unit during the Insurrection and the Human-Covenant War.[1] Its First Battalion was commanded by Lt. Colonel Ponder.