Sixty-five years ago this July, Foreign Affairs published an explosive article by diplomat George Kennan, under the pseudonym Mr. X, which isolated and defined "The Sources of Soviet Conduct." It became the centerpiece of our response to Soviet expansionism and the foundation of our Cold War policy, and made "containment" a household word and a foreign policy strategy for decades afterward.
In the article, Kennan explained that the Soviet Union's leaders were determined to spread the communist ideology around the world. Due to the "innate antagonism" between socialism and capitalism, the USSR perceived itself to be at perpetual war with the West, with no possibility for peaceful coexistence. And they were extremely patient and practical in the pursuit of that goal:
The Kremlin is under no ideological compulsion to accomplish its purposes in a hurry… The main thing is that there should always be pressure, unceasing constant pressure, toward the desired goal.