According to documentaries, there was a whole army of spies. From memory, one of the most important was a quadruple spy - the German gaseous diffusion expert w

According to documentaries, there was a whole army of spies. From memory, one of the most important was a quadruple spy - the German gaseous diffusion expert was working for the UK, USA, Germany and Russia. When FDR told Stalin about the bomb, Stalin just said, "Thank you."