Spies! Can they be stopped?
Of course! Spying will be made obsolete because, upon switching sides, you will not have sufficient rank to find out any useful information. As a private, you only know what you need to know in order to complete a mission. So, instead of “Operation Market-Garden” falling into enemy hands, all that they will know is that the “Allies are planning to destroy a bridge somewhere in the Low Countries.” And if that wasn’t enough, there’ll be a side-switch “time out” in place to prevent you from instantly switching back to your preferred side. You will have to swick with that country for an extended amount of time.