The key intelligence strategies employed by NCIS's WWII predecessors, notably the Office of Naval Intelligence (ONI) and the Naval Intelligence Service (NIS), included a diverse array of investigative methodologies aimed at combatting espionage and sabotage. Following President Franklin Roosevelt's 1939 memorandum, the focus on domestic threats forced naval intelligence agents to combine clandestine operations with the analysis of publicly available materials, such as newspapers and literature. Agents relied heavily on human intelligence (HUMINT), engaging with local communities to gather information through interpersonal relationships. For example, agents like Douglas Wada and Gero Iwai often distanced themselves from the Japanese community to maintain a low profile while still monitoring potential threats. Additionally, they utilized specialized facilities like the Black Room for processing sensitive materials, which included intercepted communications and confidential documents. This interplay of covert operations, analytical skills, and cultural sensitivity formed a comprehensive approach to intelligence gathering during the war, setting the groundwork for future developments in intelligence operations.