UNSC Marine Orbital Incursion Group

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.
Its operators are colloquially known in UNSCSOCOM parlance as "Orbital Drop Shock Troopers" (ODST), otherwise branded as "Helljumpers".
Subordinate MARORBGRU formations include the 101st ODST Battalion and the 2nd Orbital Special Warfare Battalion. The military counterterrorism team "UNSC Hostage Activity Group" is also a MARORBGRU special warfare detachment.