We had to fight the enemy without in the Falklands. We always have to be aware of the enemy within, which is much more difficult to fight and more dangerous to liberty.
When someone asked Abraham Lincoln, after he was elected president, what he was going to do about his enemies, he replied, "I am going to destroy them. I am going to make them my friends."
The end and aim of spying in all its five varieties is knowledge of the enemy; and this knowledge can only be derived, in the first instance, from the converted spy. Hence it is essential that the converted spy be treated with the utmost liberality.