The UNSC Marine Orbital Incursion Group (MARORBGRU), colloquially known as the "ODST Corps", is a special warfare division jointly operated by the UNSC Marine Corps and the UNSC Special Operations Command that specializes in special reconnaissance and orbital incursion. It is a tier-two unit in UNSC Special Operations Command, and is primarily tasked with militarized combat actions, although MARORBGRU is often used as a second choice for counterterrorism and counterinsurgency operations.