Let's say one military is sending a signal but doesn't want the other military to intercept it. Information and security are intricately linked. You want your friends to know stuff, but not your enemies, or random (previously) disinterested third parties.
The simplest solution, at first, is to only communicate when necessary. This just makes it easier for the "enemy" to determine who is communicating and devising ways to eavesdrop on that communication.
Next, you start to communicate more and more so there's noise, but then you encrypt the signals that are important to protect them against the "other". This makes the encrypted signals more interesting.
Then people formulate new ways to make and break encryption and intercept signals ad infinitum.
Go (called Wei qi, baduk or Igo in other countries), the other game I take pretty seriously, is the perfect example of this infinite simultaneous arms race.
There's a contest, it takes place on the board. One player moves, then another.
The moves aren't secret, you can see them right away. You pick the best response out of a huge number of possible lines of play.
I'm getting ahead of myself.
The game is usually played on a 19x19 grid, although beginners do better on 9x9. One player puts a black stone on an empty intersection. Another player puts a white stone on an empty intersection. If a move results in an absence of empty intersections for a stone or group of stones, it's removed. The color that surrounds the most empty space wins. You can't repeat a board position.
That's it. The rules in a nutshell, for a game that is infinitely deeper than chess. People go to school to learn this game, just in the hopes of playing it professionally. I hear the exams are brutal.
So, the thing about this game is that it's a signal/security dilemma that you can replicate anywhere. The funny thing is that there's no way to hide your moves from the other player. They're all visible, there's no way to "fool" or "trick" your opponent from the standpoint of where the actual stones are placed. You can't move them once you place them. Each one is a decision.
The modern solution to the signal/security dilemma is to forget about encrypting or protecting or limiting or obfuscating your signal.
If you have the best signal, it shouldn't matter who's listening in. Let them listen. If you're a better strategist, you already anticipated that they might know your move.
When one entity contests another, both in this metaphor and in the game, you start out operating on one of three basic assumptions:
"This opponent is weaker, I'll win easily and don't have to worry or think too much."
"This opponent is stronger, I'll play cautiously and plan for the worst, and not expect to win."
"This opponent is near my strength, this should get interesting."
Of course, sometimes you know for sure who's the better player, sometimes you don't. You'd have to play to find out.
Supposedly there was some clinical research done in China that suggested that playing Go was good for stroke rehab, and generally strengthened reasoning and judgment skills. I'd buy that.
There are few experiences that match the gravity and seriousness of a Go match. It's more similar to a martial art than a game, requiring both training and study. There is even a concept within the game called "life and death".
Anyway, enough rambling. Check out some links about Go (link, link, link)
Here are some Go pictures.