Containment was the policy adopted by the United States at the end of World War II to stop the spread of Communism beyond those areas where it then existed.
During the spring of 1945, the Soviet Union set up puppet governments in Romania and Poland in clear violation of the Yalta agreements. Stalin justified this by claiming that the U.S. had negotiated German surrender behind his back, and German forces were now concentrated against the Soviet Union. Later, the Soviets refused to withdraw from East Germany, and set up a puppet government there also. Stalin stated in 1946 that peace was impossible under the present Capitalist development of the world economy." It became apparent that the Soviets were intent on world domination and the destruction of Western capitalism. George F. Kennan, former ambassador to Moscow, wrote an anonymous article for a magazine in which he stated that the Soviets intended to
fill every nook and cranny available in the basin of world power
He stated that the United States policy must be a
long term, patient but firm and vigilant containment of Russian expansive tendencies…. Such a policy has nothing to do with outward histrionics: with threats or blustering or superfluous gestures of outward toughness."
Thus was born the policy of Containment.