George Frost Kennan served a very short tour of Ambassador - less than a year - but his ideas, particularly the doctrine of "containment," had a powerful influence on future U.S.-Soviet relations. Born in Milwaukee, Wisconsin, he graduated from Princeton University in 1925 with a degree in History, and entered the Foreign Service the following year. In 1933, he was an aide to Ambassador Bullitt in Moscow when the Embassy opened there. From 1944 to 1946, he was Minister Counselor in Moscow, and Charge d'Affaires after Ambassador Harriman left post in January 1946. In February 1946, he wrote his famous "Long Telegram," calling for a policy of containment of Soviet expansion. In 1947, he became Director of the State Department's Policy Planning Staff, and then adviser to Secretary of State Dean Acheson. President Truman named him Ambassador to Moscow, and he presented his credentials on May 14, 1952. While he was out of the country in October 1952, Kennan was declared persona non grata by the Soviet Government for remarks critical of Stalin, and he did not return. He retired from the Foreign Service the following year, and became a Professor at Princeton, where he wrote many influential books about Russian-American relations and foreign policy.