Donald Henry Rumsfeld (born July 9, 1932) is a United States businessman, politician, who served as the 13th Secretary of Defense under President Gerald Ford from 1975 to 1977, and as the 21st Secretary of Defense under President George W. Bush from 2001 to 2006. He is both the youngest (43 years old) and the oldest (74 years old) person to have served as Secretary of Defense, as well as the only person to have served in the position for two non-consecutive terms. Overall, he was the second longest serving defense secretary behind Robert McNamara. Rumsfeld was White House Chief of Staff during part of the Ford Administration, and also served in various positions in the Nixon Administration. He served four terms in the United States House of Representatives, and served as United States Ambassador to NATO. He was an aviator in the United States Navy between 1954 and 1957 before transferring to the Reserve. In public life, he has served as an official in numerous federal commissions and councils.