These are the different branches that exist within the Office of Naval Intelligence.
“The UNSC Prowler Corps is a subbranch of the UNSC Navy. All permanent crew aboard UNSC prowlers...UNSC Prowler Corps
“ONI Section One is a subdivision of the Office of Naval Intelligence. It is the branch most...ONI Section One
“ONI Section Zero is a subdivision of the Office of Naval Intelligence. Starting in at least...ONI Section Zero
“The ONI Signal Corps is a sub-branch of the ONI, staffed by members of the UNSC Navy and Marine...ONI Signal Corps