The Defense Force is the entire military branch for the ONI CC. The Defense force consists of the Navy, the Army, the Air Force, and the Marine Corps. These sub-branches all work in unison, and in joint operations, to ensure the security and the protection of all human interests. The Defense Force has been the face of the military since the formation of the UNSC, and will continue to be the face of the military in the years ahead.
The Defense Force served the same role in both The UNSC and The ONI CC.