We know there were a few soviet spys involved in the product but we also know it 100's of people took a part of the project. Maybe not many knew what they were working on and knew what they were developing. Outside of the Soviet spys and how many ci illians supported the mission,how was the US able to keep the Manhattan project so secret or if I'm wrong (again minus the Soviet spys) how did they screw up protecting the research and production?
Very tight and heavy security along with compartmentalization. Only a few people knew the real reason for the project. Most of the people who worked on the project only knew about the small part of the project they were involved with. More information on Manhattan Project Security here: http://www.atomicheritage.org/history/security-and-secrecy