What is the primary mission of NCIS?

The primary mission of the Naval Criminal Investigative Service (NCIS) is to protect and defend the Department of the Navy (DON) against terrorism while also investigating major offenses. This encompasses a wide range of responsibilities, including counterterrorism efforts, criminal investigations, and protective services, all aimed at ensuring the safety and security of Navy and Marine Corps personnel, assets, and operations.

The focus on both protection from terrorism and investigation of serious crimes reflects the agency's role as a critical component of naval security. By addressing threats before they materialize and responding effectively to incidents that do occur, NCIS plays a vital part in maintaining the overall integrity of Navy and Marine Corps operations.

Other options may touch on certain aspects of NCIS functions, such as enforcing laws or coordinating with civilian law enforcement, but they do not encapsulate the comprehensive mission of protecting against terrorism and investigating significant criminal activities as effectively as the correct option does.