Petty Officer, Second Class
From Halopedia, the Halo wiki
Petty Officer, Second Class, abbreviated to PO2, is an enlisted rank in the United Nations Space Command Naval Command (NAVCOM) rank structure; including the UNSC Navy and Office of Naval Intelligence. It is preceded by Petty Officer Third Class, and subordinate to a Petty Officer First Class.
- Halo: Official Spartan Field Manual - PART 8: UNSC ORGANISATION, NAVCOM Ranks, page 140-141