The Pearl Harbor attack was pivotal in shaping modern NCIS as it highlighted the need for a dedicated agency to address domestic counterespionage and national security threats. Following the attack, it became clear that effective intelligence operations were crucial to prevent similar attacks, prompting the Navy to enhance its focus on intelligence gathering and counterintelligence activities. The Office of Naval Intelligence (ONI), which was established in the late 19th century, expanded its efforts in response to the vulnerabilities exposed during the attack. This transition laid the groundwork for the formation of the Naval Investigative Service (NIS), the predecessor of NCIS, emphasizing the importance of both investigation and intelligence in naval operations. The lessons learned from Pearl Harbor are central to the agency's foundational history, underscoring how key events influence the evolution and strategies of intelligence organizations. Ultimately, the attack served as a catalyst for the establishment and growth of NCIS, focusing on a broader mandate encompassing counterespionage and security in the post-war era.