The Yalta Conference (February 1944) is generally taken as the Cold War's starting point. In reality this war had started long before the Second World War. Indeed, it has been waged stealthily for more than two decades by the Sovient Union. The United States started taking serious countermeasures to the KGB's spies and other secret agents as late at 1946. This article summarizes this secret war's main episodes and consequences.
AFTALION, F. (2008). La guerre froide sur le sol américain. Histoire et liberté, (36), pp. 33-40.