George Catlett Marshall ( December 31 , 1880 -- October 16 , 1959 ) was an American military leader , Chief of Staff of the Army , Secretary of State , and the third Secretary of Defense . George Catlett Marshall ( December 31 , 1880 â `` October 16 , 1959 ) was an American military leader , Chief of Staff of the Army , Secretary of State , and the third Secretary of Defense .