Final answer:
If you're in the U.S. Navy, you're part of the Department of Defense, which handles national security and armed forces. The Department of Homeland Security has different focuses, like border security. The Department of State manages foreign policy, but Defense contributes significantly to military aspects of foreign policy.
Step-by-step explanation:
If you're a member of the U.S. Navy, your organization is part of the Department of Defense. The Department of Defense is responsible for coordinating and supervising all agencies and functions of the government related directly to national security and the United States armed forces. The Department of Defense's main functions include advancing national defense, which encompasses operating the military branches (Army, Navy, Air Force, and Marine Corps), and overseeing entities responsible for defense research and development. Other departments, such as the Department of Transportation, Department of Commerce, and Department of the Interior, have different focuses such as helping industries stay strong, protecting the environment, and helping workers as a group, which are not directly related to the nation's defense.
In contrast, the Department of Homeland Security is a separate entity with duties including guarding U.S. borders and managing various law enforcement agencies including the Coast Guard, Secret Service, and U.S. Customs. Both the Departments of Defense and Homeland Security play critical roles in maintaining the nation's security but have distinct functions and areas of responsibility.
In relation to U.S. foreign policy, the executive department primarily responsible is the Department of State, which manages international relations. However, the Department of Defense also plays a significant role in foreign policy since military strategy and the use of armed forces can be critical components of a nation's international strategy as theorized by figures like Mahan, who emphasized the importance of a strong navy and military presence to build an American empire.