Born in Milwaukee, Wisconsin to Kossuth Kennan and Florence James Kennan, he attended Saint John’s Military Academy and then Princeton University, graduating in 1925 and entering the diplomatic corps.
His first assignment was to Geneva, moving to Hamburg in 1927 and Tallinn in 1928; the following year he was assigned as third secretary attached to all of the Baltic republics. In 1931 he married the Norwegian Annaliese Sorenson, the same year he began the study of Russian language and culture at Berlin, part of a State Department effort to prepare for US recognition of the Soviet Union.
When the US embassy reopened in Moscow in 1933, Kennan went along with Ambassador William Bullitt, where he served until 1937. He then spent a year in the US, a year in Prague, then to the US embassy in Berlin, where in 1940 as first secretary to Sumner Welles he tried to help develop a peace settlement. He was in Berlin when the US declared war on Nazi Germany, and was interned for several month, returning to the States in May 1942.
During the war, he represented in US in Portugal, and was part of the delegation to the European Advisory Commission, then in 1944 returned to the embassy in Moscow.
In 1947, George C. Marshall put Kennan in charge of policy planning at the State Department, where Kennan advocated the containment policy, most famously with an anonymous article, titled "The Sources of Soviet Conduct" but more famously known as the X article, in the July 1947 Foreign Affairs. He was appointed Ambassador to the Soviet Union in 1952, but was recalled in October when remarks in Berlin caused a diplomatic incident. Specifically, Kennan compared the Soviet Union to Nazi Germany. For this he was dubbed "persona non grata."
Kennan retired from the Foreign Service in 1953, and joined the Institute for Advanced Study in Princeton, where he remained until retirement (except for a 1961-63 stint as ambassador to Yugoslavia), winning note for a number of books and articles, including Pulitzer Prizes for Russia Leaves the War and Memoirs.
See also: Origins of the Cold War