US Army Center
U.s. Army Center of Military History: Peace Becomes Cold War, 1945 1950
A discussion of historical events that led to the Cold War from the perspective of the U.S. Army. Particular emphasis is placed on military leadership and policy.
Other
The Office of the Secretary of Defense
A great site to obtain basic understanding of the office of the Secretary of Defense. Clicking on "The Office of the Secretary of Defense" will bring up pictures of the Secretary and his/her assistants.
Wikimedia
Wikipedia: Donald Rumsfeld
A detailed biography of past Secretary of Defense Donald Rumsfeld, excellent as a starting point to begin research.
Other
Richard B. Cheney, 17th Secretary of Defense
Detailed account of Cheney's term as Secretary of Defense under President George H. W. Bush.
Harry S. Truman Library and Museum
Harry S. Truman Library: The President's Cabinet
Features a teacher-directed activity that explores the President's Cabinet and the duties of each secretary.