It might have been the most influential single sentence of that era: "In these circumstances it is clear that the main element of any United States policy toward the Soviet Union must be that of long-term, patient but firm and vigilant containment of Russian expansive tendencies." And it originated in an 8,000 word telegram -- yes, in those days, unbelievably enough, there was no email, no Internet, no Snapchat, no Facebook -- sent back to Washington in February 1946 by George F. Kennan, the U.S. chargé d'affaires in Moscow, at a moment when the Cold War between the United States and the Soviet Union was just gaining traction.
The next year, a reworked version of Kennan's "Long Telegram" with that sentence would be published as "The Sources of Soviet Conduct" in the prestigious magazine Foreign Affairs under the pseudonym "Mr. X" (though it was common knowledge in Washington who had written it). From that moment on, "containment" of what, until the Sino-Soviet split, was called the Soviet bloc, would be Washington's signature foreign and military policy of the era. The idea was to ring the Soviet Union and China with bases and then militarily, economically, and diplomatically hem in a gaggle of communist states from Hungary and Czechoslovakia in Eastern Europe to North Korea on the Pacific and from Siberia south to the Central Asian SSRs of the Soviet Union. In other words, much of the Eurasian land mass.