When nuclear fission was discovered in 1938, it was soon realized that this might be the mechanism to produce the neutrons for the chain reaction, if the process also produced neutrons, and this was proven in 1939, making the path to nuclear power production evident.
This might be the mechanism to produce the neutrons for the chain reaction, if the process also produced neutrons. This was soon realized. Nuclear fission was discovered in 1938. This was proven in 1939. This was making the path to nuclear power production evident.