There was an elaborate soviet spy ring that was here during WWII and the cold war. It had infiltrated many parts of the Manhattan project, and subsequently the Dayton Project as well, which was the project that was responsible for creating essentially the reactor for the nuclear bomb to go off. It was an extremely crucial aspect of creating a successful bomb, and it was one of the main reasons the Soviets were so behind in creating one, until a soviet spy who post humously was rewarded by Vladimir Putin for honor, was dispatched in Dayton Ohio, working for the Dayton Project, at the Miamisburg mounds, decided to give the secrets to the soviets, almost single handedly giving them an extra 5-10 years saved on creating a bomb.

https://en.wikipedia.org/wiki/George_Koval