George Kennan sends the 'Long Telegram'
The Long Telegram [backup link] was an 8,000 word telegram sent by Kennan (a US diplomat in Moscow) to the US Government. Kennan advocated a policy of containment be adopted in relation to the USSR.
Kennan suggested that the USSR lived in a world of "capitalist encirclement," claiming in a 1927 speech to a delegation of American workers Stalin had made clear he thought that it was inevitable that countries would gravitate two "centres" (a "socialist center" and a "capitalist center"). Kennan suggested that the USSR believed moderate left-wing socialists to be a greater enemy than capitalists.
His [Kennan's] belief was that the people of the USSR's views did not coincide with those of the regime. Kennan urged the USA to adopt a policy of containment of communism.