Final answer:
Davis could have originally been part of any military branch except for the Navy, as he was transferred there during a national emergency. The military branches include the Army, Air Force, Marine Corps, Coast Guard, and National Guard, and are all under civilian control by the President and overseen by the Department of Defense.
Step-by-step explanation:
The U.S. armed forces consist of various branches including the Army, Navy, Marine Corps, Air Force, and Coast Guard. During national emergencies, personnel may be transferred between different branches. If Davis was transferred to the Navy during such a time, it indicates that he was originally a part of a different military branch than the Navy, which could be the Army, National Guard, Marine Corps, Air Force, or Coast Guard.
The other branches mentioned, such as the Army, Air Force, and National Guard, could see their members transferred to the Navy in a time of need. While the Marine Corps often works closely with the Navy, they are a distinct branch and thus it is also possible for Marine Corps personnel to be reassigned to the Navy. The Coast Guard, which can operate under the Department of Homeland Security or the Department of the Navy during wartime, is another potential original branch for Davis.
However, without specific information on Davis's original role or branch, determining his exact original branch requires more context or information. The military branches are under the civilian control of the President, who is the Commander in Chief, and they were all reorganized under the Department of Defense in 1949.