|'Containment of the Soviet Union became American policy in the postwar years. George Kennan, a top official at the U.S. embassy in Moscow, defined the new approach in the Long Telegram he sent to the State Department in 1946. He extended his analysis in an article under the signature "X" in the prestigious journal Foreign Affairs. Pointing to Russia's traditional sense of insecurity, Kennan argued that the Soviet Union would not soften its stance under any circumstances. Moscow, he wrote, was "committed fanatically to the belief that with the United States there can be no permanent modus vivendi, that it is desirable and necessary that the internal harmony of our society be disrupted." Moscow's pressure to expand its power had to be stopped through "firm and vigilant containment of Russian expansive tendencies. ..."'