From Halopedia, the Halo wiki
SURGEON is a code name adopted by an Office of Naval Intelligence operative with Section III. This operative's Section III Operator Number is AA2. Notably, SURGEON served in a leadership capacity in Operation: HYPODERMIC and frequently exchanged secure transmissions with Codename: COALMINER.
The earliest known activity from SURGEON was in 2532, when he/she received a message concerning the SPARTAN-III program from Codename: COALMINER. The message noted that the early stages of preparation for SPARTAN-III Alpha Company were progressing satisfactorily and expressed confidence in Kurt-051's training regimen.
SURGEON was later informed by Codename: COALMINER of a potential breach of security when Cortana broke into the ONI database and discovered that the UNSC Circumference was an ONI Prowler. COALMINER then deleted the ship from the Reach database. 
On December 31, 2552, SURGEON filed a report to Codename: USUAL SUSPECTS entitled "Historical/Psychological Analysis of Cole, Preston J." The extensive report outlined the life and career of Admiral Preston J. Cole and postulated that he was in fact alive and living outside UNSC-controlled space. The report was filed from the UNSC Point of No Return in synchronous orbit on the far side of Luna.
After a terrorist attack on the human colony of Sedra in early February of 2556, SURGEON received a report made by Codename: FIXER about the story of the Alerian mining union Mols'Desias, and mentioning the Sedran medic Brynn Morad trying to get access to Indrid Lota's medic file.
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