The Game is question is a "pretend nations" game.
Each participant controls a fantasy nation on a map.
Each nation has a randomly determined power level and the player for each nation breaks down their power points into armies, ambassadors, wizards etc.
The way the ruling player makes moves is that they write a letter to the DM, In-Character, as of they were the ruler writing to the generals of their armies, their intelligence head, ambassador etc, sending instructions, asking for information etc.
They write one of these per month, though within that can address as many of their pre-created individuals as they wish, so one letter can have one part going to the head of an army and another sheet going to the high priest or whatever.
During the month, the DM resolves the results of any interactions between nations. I'm thinking here specifically of the results of a battle between armies but a very wide range of interactions are possible. They then write letters back to each ruler, in the voice of their generals or wizards or whatever, telling them what happened, from that characters point of view.
Players are also allowed to write to each other, in-character, if they want to, but they are meant to only do it in hardcopy.
The world creation is set up so that nations have access to each other but up until the opening state of play, have had very little ability to interact, and so they each know each others nations exist and a little about them but don't have much in-depth information.
The world has also been set up so that a major stabilising central authority has just dispensary. This is intended to lead to conflict and creative interaction.
The problem is this;When players create intelligence agents, ambassadors and other infiltrators, and send them into each others territory, I'm not sure how to handle it.
The world creation is somewhat emergent, people don't define every hex of their nation to begin with, we are making up details as they come into play.
And the DM (me) isn't supposed to tell different players what the others are up to, unless their agents, or the people of their nation, can observe it.
So when player A sends a spy into player B's territory, how do I decide what to tell them?
I could just make parts of it up, but that means I am making up details about someone's country. If I do that I *have* to tell them what those details are ultimately. And if I go around telling people; "Oh you have a thriving but corrupt port city here" that might be bearable, but it also lets them know they are being spied on, because content has been generated.
I could ask the player being spied on for the information; "Hey do you have a city hereabouts and what in general do you think might be there?" That lets them keep control of their own nation but also, again, lets them know they are being spied on.
I could organise some "baffling" process where each month I ask each of them a random question about the makeup of their nation, and some of those might be for spies from other nations, but many will just be random?
I am OPEN TO IDEAS for solutions to this unusual problem.