George F. Kennan

From Wikipedia:

George Frost Kennan (February 16, 1904 – March 17, 2005) was an American advisor, diplomat, political scientist, and historian, best known as "the father of containment" and as a key figure in the emergence of the Cold War. He later wrote standard histories of the relations between Russia and the Western powers.

In the late 1940s, his writings inspired the Truman Doctrine and the U.S. foreign policy of "containing" the Soviet Union, thrusting him into a lifelong role as a leading authority on the Cold War. His "Long Telegram" from Moscow in 1946, and the subsequent 1947 article "The Sources of Soviet Conduct" argued that the Soviet regime was inherently expansionist and that its influence had to be "contained" in areas of vital strategic importance to the United States. These texts quickly emerged as foundational texts of the Cold War, expressing the Truman administration's new anti-Soviet Union policy. Kennan also played a leading role in the development of definitive Cold War programs and institutions, most notably the Marshall Plan.

Shortly after the diploma had been enshrined as official U.S. policy, Kennan began to criticize the policies that he had seemingly helped launch. By mid-1948, he was convinced that the situation in Western Europe had improved to the point where negotiations could be initiated with Moscow. The suggestion did not resonate within the Truman administration, and Kennan's influence was increasingly marginalized—particularly after Dean Acheson was appointed Secretary of State in 1949. As U.S. Cold War strategy assumed a more aggressive and militaristic tone, Kennan bemoaned what he called a misinterpretation of his thinking.

In 1950, Kennan left the Department of State, except for two brief ambassadorial stints in Moscow and Yugoslavia, and became a leading realist critic of U.S. foreign policy. He continued to be a leading thinker in international affairs as a faculty member of the Institute for Advanced Study from 1956 until his death at age 101 in March 2005.