Harry Truman actually said...
The Secretary of State, the Secretary of War, the Attorney General, and the Secretary of the Navy are authorized to provide appropriate assistance to the members and the alternate member herein designated in the performance of their duties and may assign or detail such personnel under their respective jurisdiction, including members of the armed forces, as may be requested for the purpose.
Context
Executive Order 9827—Appointment of the Members and the Alternate Member of a Military Tribunal Established for the Trial...
02/20/1947