RDS-37 was the Soviet Union's first two-stage hydrogen bomb, first tested on 22 November 1955. The weapon had a nominal yield of approximately 3 megatons. It was scaled down to 1.6 megatons for the live test. Leading to the RDS-37 The RDS-37 was a reaction to the efforts of the United States. Previously, the Soviet Union allegedly used many of their spies in the U.S. to help them generate methods and ideas for the nuclear bomb. The creation of the hydrogen bomb required less usage of this method, although they still received help from some spies, most importantly, Klaus Fuchs. In 1945, the Soviet Union reached a decision to work on a design for a "super bomb". Also in 1945, Enrico Fermi gave lectures at Los Alamos discussing the fusion process. At the end of his lecture he stated "so far all schemes for the initiation of the super [are] rather vague". In the spring of 1946, Edward Teller set up a conference to assess all the information known about the hydrogen bomb. Klaus Fuchs attended this same conference. In the same year, Teller postulated a new design for the hydrogen bomb, which he called the "Alarm Clock", which he suggested would use lithium-6 deuteride instead of pure deuterium. Klaus Fuchs had passed on information about both the nuclear bomb and the hydrogen bomb to the Soviet Union. This information resulted in the recruitment of Igor Tamm’s group, whose work helped create the hydrogen bomb. The content that Fuchs provided in 1948 was not only related to the hydrogen bomb, but also the nuclear industry as a whole. It provided detailed insight into the bomb design using a two-stage igniting block. The designs were quickly sent to Lavrentiy Beria, who had been placed in charge of the Russian bomb program by Joseph Stalin and forwarded to Igor Kurchatov, Boris Vannikov and Yulii Khariton, to validate and assess these designs. On May 5, 1948, Vannikov and Kurchatov wrote a reply, stating: As regards the material No. 713a, the basic ideas about the role of tritium in the transfer of explosion from a uranium-235 primer to deuterium, about the necessity of careful selection of uranium primer power, and about the role of particles and photons in the transfer of the explosion to deuterium are new. These materials are valuable in that they will be helpful to Cde. Zel’dovich in his work on