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"Tasked with uncovering disloyalty and inefficiency, this branch reports all infractions directly to the central ISB hub on Coruscant."
Admiral Wullf Yularen describes the Surveillance branch, Imperial Handbook: A Commander's Guide[2]

Surveillance was a branch of the Imperial Security Bureau. The largest branch within the ISB, Surveillance accounted for almost thirty-five percent of the Bureau's manpower. The personnel from Surveillance were generally drawn from Sub-Adult Groups, CompForce Observers, veteran officials from the Sector Monitors, or personnel from Sector Development. Surveillance's mandate was to uncover those individuals or activities that would either pose a threat to the Galactic Empire and its operations, or assist its enemies, such as the Alliance to Restore the Republic. If sufficient evidence in either case was found, the matter was turned over to Investigations for further action. Surveillance was also employed as a deterrent; the citizen's fear of the branch and the Galactic Empire stopped many from supporting the Rebellion.[1]

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