Final answer:
The Secretary of War was historically in charge of the U.S. Army and matters of war. Now replaced by the Secretary of Defense, this position is responsible for defense matters, overseeing military policy and operations, and contributing to foreign policy.
Step-by-step explanation:
The Secretary of War, a historic title that was used for the head of the Department of War, was a cabinet position responsible for the matters pertaining to war and the United States Army. In the modern context, this role has been succeeded by the Secretary of Defense who now heads the Department of Defense.
The Secretary of Defense is a key cabinet member for foreign policy, serves as the civilian head of the armed services, and provides advice to the President on defense matters, oversees military policy and operations, and has a significant role in foreign affairs, particularly in deploying troops and managing crises.
The Department of Defense is a vast bureaucracy with many sub-departments and offices, and the Secretary's role extends beyond merely handling the military aspects of the nation to include broader foreign policy objectives. In addition, the Secretary of Defense along with the Secretary of State and the Secretary of Homeland Security, form critical components of the President's foreign policy team and help shape the nation's defense strategies and international relations.