Playing late into my game as France and I realized that spies now have the ability to set up "Spy Networks" in regions.
If a spy is successful and stays in a city for 2-4 turns then he'll eventually set up a network that allows you to see the entire region. This I find very useful and makes Spies an actual useful agent on the field.
Though my question because I haven't tried it yet but how long do these networks last for? If I move my spy to another city will the network eventually disappear?