William D. Leahy

William D. Leahy
Leahy c. 1945
Chief of Staff to the Commander in Chief
In office July 20, 1942 – March 21, 1949
President	Franklin D. Roosevelt Harry S. Truman
Preceded by	Office established
Succeeded by	Omar Bradley (as Chairman of the Joint Chiefs of Staff)
United States Ambassador to France
In office January 8, 1941 – May 1, 1942
President	Franklin D. Roosevelt
Preceded by	William Christian Bullitt Jr.
Succeeded by	Jefferson Caffery
Governor of Puerto Rico
In office September 11, 1939 – November 28, 1940
President	Franklin D. Roosevelt
Preceded by	Blanton Winship
Succeeded by	Rexford Tugwell
Chief of Naval Operations
In office January 2, 1937 – August 1, 1939
President	Franklin D. Roosevelt
Preceded by	William Harrison Standley
Succeeded by	Harold Rainsford Stark
Personal details
Born	William Daniel Leahy (1875-05-06)May 6, 1875 Hampton, Iowa, U.S.
Died	July 20, 1959(1959-07-20) (aged 84) Bethesda, Maryland, U.S.
Resting place	Arlington National Cemetery
Relations	William Harrington Leahy (son)
Military service
Branch/service	United States Navy
Years of service	1893–1959
Rank	Fleet Admiral
Commands	Chief of Staff to the Commander in Chief Chief of Naval Operations Battleships Battle Force USS New Mexico USS Shawmut USS St. Louis USS Chattanooga USS Princess Matoika USS Dolphin USS Mariveles
Battles/wars	Spanish–American War Philippine–American War Boxer Rebellion World War I Occupation of Nicaragua Occupation of Haiti Occupation of the Dominican Republic World War II
Awards	Navy Cross Navy Distinguished Service Medal (3)

William Daniel Leahy (/ˈleɪhiˌ ˈleɪ.i/) (May 6, 1875 – July 20, 1959) was an American naval officer. The most senior United States military officer on active duty during World War II, he held several titles and exercised considerable influence over foreign and military policy. As a fleet admiral, he was the first flag officer ever to hold a five-star rank in the U.S. Armed Forces.

An 1897 graduate of Annapolis, Leahy saw active service in the Spanish–American War, the Philippine–American War, the Boxer Rebellion in China, the Banana Wars in Central America, and World War I. He was the first member of his cadet class to reach flag rank, as the Chief of the Bureau of Ordnance from 1927 to 1931. He subsequently served as Chief of the Bureau of Navigation from 1933 to 1936, and commanded the Battle Fleet from 1936 to 1937. As Chief of Naval Operations from 1937 to 1939, he was the senior officer in the United States Navy, overseeing the expansion of the fleet and preparations for war.

After retiring from the Navy, Leahy was appointed the governor of Puerto Rico in 1939 by President Franklin D. Roosevelt. In his most controversial role, he served as the Ambassador to France from 1940 to 1942. American policy was aimed at keeping the government of Vichy France free of German control, but Leahy had limited success. He came to believe that the United States should back Free France instead of Vichy France, and asked to be recalled after the Japanese attack on Pearl Harbor brought the United States into the war.

Leahy was recalled to active duty as the Chief of Staff to the President in 1942 and served in that position for the rest of the war. He was the highest-ranking active-duty member of the military. As the de facto first Chairman of the Joint Chiefs of Staff, he oversaw all of the American armed forces. He also presided over the American delegation to the Combined Chiefs of Staff. He was a major decision-maker during the war and was second only to the President in authority and influence. Leahy was promoted to five-star rank in December 1944. He served Roosevelt's successor Harry S. Truman, helping shape postwar foreign policy until he retired in 1949. Although he did not oppose the use of the nuclear weapons during the war, in the post-war period he rejected war plans that placed too much emphasis on the first use of nuclear weapons.