In January 1933, the Nazis came to power in Germany and suppressed Jewish scientists. Like many others Leó Szilárd fled to London where in 1934, he patented the idea of a nuclear chain reaction via neutrons. The patent also introduced the term critical mass to describe the minimum amount of material required to sustain the chain reaction and its potential to cause an explosion (British patent 630,726). The patent was not about an atomic bomb "per se", as the possibility of chain reaction was still very speculative. Szilard subsequently assigned the patent to the British Admiralty so that it could be covered by the Official Secrets Act. In a very real sense, Szilárd was the father of the atomic bomb academically.