America's most influential diplomat of the twentieth century, George F. Kennan, has died at his home in Princeton, N.J. at the age of 101. Kennan is best remembered as the author of the "Long Telegram" and the Mr. X article, an essay in the July 1947 issue of Foreign Affairs entitled "The Sources of Soviet Conduct." These two documents were instrumental in establishing the intellectual foundations of the American policy of containment.
Here's the obituary in the New York Times.