In retrospect, the CIA assesses its huge failure to accurately predict when the Soviet Union would explode an atomic bomb as follows:
“In the end, US experience, however valid it might be from a scientific or technological point of view, did not offer a valid timeline for Soviet nuclear development. It failed to allow for whatever benefits the Soviets derived from information made public after the war, from espionage, from the input from captured and “immigrant” German scientists, and from the incalculable advantage they had in knowing with absolute certainty that the thing could be made to work! In retrospect, it seems that [the Office of Reports and Estimates’] failure to accurately predict the advent of the Soviet atomic bomb was due less to any particular shortcoming than a general failure to piece everything together.”
You may find the whole report as dull as the proverbial dishwater, but scan an additional paragraph or two here. Does this inspire much confidence in the intelligence capacities of the early Cold War United States? In 1949, how much did the United States actually know about the rest of the world?