How Did the Spy Networks Work in the Second World War?

Many of those that served in intelligence were linked to particular forces. They could find themselves in any branch of military intelligence. In some cases, they were useful for helping to run the deception operations from London. And in other cases, they would be dropped behind enemy lines. But essentially you're not heading down to the recruiting office and saying, I volunteered to be a spy. No, in fact, one of the double agents did that. And they thought he was a German plant.