From Halopedia, the Halo wiki
Branch:
UNSC Marine Corps
Type:
Rifle Company
Role:
Locate close with and destroy the enemy by fire and maneuver and repel the enemy's assault by fire and close combat
Size:
100-150 Marines
Alpha Company is a UNSC Marine Corps unit that fought during the Battle of Voi and the Battle of Installation 00 with the Master Chief and the Arbiter in late 2552 [1].