The "long telegram" was an 8,000-page memorandum by George Kennan, the Deputy Chief of Mission to the U.S. Embassy in Moscow, detailing the post-war attitudes and plans of the Soviet Union. Written in February 1946, the document helped shape the policy of containment of communism adopted by Truman and subsequently carried on by other administrations.
George Kennan had been working at the American embassy in Moscow since its establishment in 1933 and was deeply familiar with the history and culture of the Russian people. During World War II, he felt that the cooperation of President Franklin Roosevelt with Joseph Stalin of Russia was a mistake. Kennan wrote his telegram shortly after Truman took office following Roosevelt's death.
In the telegram, Kennan pointed out the negative attitude of the Soviets towards capitalistic powers, the Soviet government's antipathy towards non-communist left-wing groups in its own country and its plan to use Marxist groups in the West to further its cause. He claimed that, by its nature, the Soviet government was unable to separate objective reality from the fantasies of its own propaganda, but though it could not be reasoned with logically, it could be dealt with by threat of force. He reasoned that the Russian phobia against peaceful coexistence with the West stemmed from the Russian people's innate sense of insecurity.