Fleet admiral, classified under the pay grade O-10, is the highest rank obtainable in the United States Navy. Created during the 1940s, this rank has only been held by a select few officers and is incredibly difficult to obtain.
The rank of fleet admiral was created in 1944 by Congress under President Harry Truman during World War II. Only four people have ever held the rank: Chester W. Nimitz, William D. Leahy, Ernest J. King and William F. Halsey, Jr. Each of these admirals served during World War II and was nominated by Truman himself.
The rank of fleet admiral was designed to provide firm leadership in a rapidly expanding and highly mobilized Navy. It represents the highest leadership position possible in the Navy, and is equivalent to the ranks of General of the Army and General of the Air Force in the military's other main branches. Note that fleet admirals are also ultimately in charge of the Marine Corps and Coast Guard as the highest-ranking officer within the Department of the Navy.
While the rank of fleet admiral still technically exists, it is impossible to obtain unless it is reactivated during a time of war or crisis. As of 2010, there is still no presidential authority to promote officers in the Navy to the grade of O-10. That authority expired, according to the original bill creating the rank, six months after the end of World War II.
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