The detonation of a bomb on Russian soil prompted the United States to take steps to protect itself from Soviet espionage,
In 1949, the Americans were shocked after seeing that the U.S.S.R. had detonated an atomic bomb they were testing in their soils. It had occured only 4 years since the detonation of the atomic bombs of Hiroshima and Nagasaki. At that time, nearly a dozen Soviet spies were convicted of passing information to the Soviets during this period about the atomic bomb in what is known as the "Manhattan Project", the most famous spy being Emil Julius Klaus Fuchs. After this experience, the United States devoted a large quantity of money in protecting their secret projects and fighting espionage.
Other reasons that led US to protect from espionage were defeat of the Nationalist by Communists in China, the Korean War and the conviction of Alger Hiss.