The USSR successfully tested an atomic bomb in August 1949. I remember reading that the USA was expecting to loose their atomic monopoly later than that, so it came as a surprise in 1949. When were the USA expecting this, and what was the document/statement called which said this.
I tried Google, couldn't find anything.
There were different estimates as to when the Soviet Union would acquire atomic weapons. In 1945, the scientists estimated 5-10 years, many leaning towards just 5 years. Some of the military men, like General Groves, thought it would take 20 years. These estimates never got "updated" — so it was 5 years in 1945, 5 years in 1946, 5 years in 1947, 5 years in 1948, 5 years in 1949. So in 1949 a lot of people said they got it 5 years early. In reality, it took them about 4 years to get the bomb, so at most they maybe got it a year earlier than they had guessed in 1945. But the Americans had essentially no intelligence information on when the USSR nuclear program until the mid-1950s, so they were really just guessing somewhat wildly based on expectations as to what the USSR was willing to spend and how hard it would be for them to develop the relevant facilities.
There is no single document with these estimates. Some were made confidentially, some were made in Congress. The best book on this topic is Michael Gordin's Red Cloud at Dawn, which has a whole chapter called "Estimates."