I would think if it lets you place a spy in his city conducting intelligence, sabotage, or corruption then you probably have an answer. If it allows it then i would assume he can discover your spy just like anyone else. But that is just my guess...not fact.

You can spy on your allies if you are talking about in-game coalitions.

However, each spy has a chance to get caught, and some will also tell who they worked for which would mean that that player has a good chance to know you were responsible for said spy.

Also, with spies they can each either fail or succeed at a mission and not always going to give you something useful like their messages, and those messages could be from a period of time that may be outside of the time they were in your coalition.

One thing is if you are in a coalition just pay attention to the players in questions actions and it might give you more info then spies.

Examples: If they suddenly start amassing a huge number of troops on your border it is possible they are ready to invade you.

@ riccz just kill the lying backstabbing piece of $#!%...and have fun doing it!

sometimes you need to . Once I was playing Myanmar and had India , Japan , China as allies . Only India responded to my messages and Japan , our leader , never provided help and just played his own game . I spied him and found that he had given RoW to our coalition's enemy , Philippines and was probably telling him troop placements too .

But are they going to see your intelligence like they do, when you spy someone outside? And what about other coalition members?

If you put intelligence spies in their cities yep, they will see the information on their intelligence panel