The Department of Defense handles which aspect of national security?

The Department of Defense is primarily responsible for the armed protection of the United States. This includes overseeing the military branches—such as the Army, Navy, Air Force, and Marines—and ensuring they are prepared to respond to national security threats. The department's duties encompass a range of activities, including defense policy formulation, military readiness, and conducting military operations to protect the nation's interests both domestically and abroad.

National security is fundamentally about maintaining the integrity, sovereignty, and safety of the nation against external threats, which the Department of Defense directly addresses through its military capabilities. By concentrating on armed protection, the Department of Defense plays a critical role in deterring potential adversaries and responding effectively should conflict arise.

Other areas like financial, health, and environmental security, while important components of overall national well-being, fall outside the scope of the Department of Defense's responsibilities. These areas are typically managed by other government departments or agencies that focus on those specific domains of security.