For more than 210 years, the Coast Guard has served the nation as one of the five armed forces. Throughout its distinguished history, the Coast Guard has enjoyed a unique relationship with the Navy. By statute, the Coast Guard is an armed force, operating in the joint arena at any time and functioning as a specialized service under the Navy in time of war or when directed by the President. It also has command responsibilities for the U.S. Maritime Defense Zone, countering potential threats to American's coasts, ports, and inland waterways through numerous port-security, harbor-defense, and coastal-warfare operations and exercises.