@ maddman75
If you want to give a % chance to become a prisoner, make the more advanced a bigger one. WHY !!! would you say. Because, I don't remember romans or greecs to make a lot of prisoners in the ancient times. Nowadays, soldiers are not as "die for the country" as they were then. They prefer to be prisoners than to die ...
But generaly, the concept is ok for me. But the big question is : "What becomes of the prisoners ?". Yes, killing them would be an option (especially in ancient times), but the closer to modern days you are, the more options there should be. The second option would be to slave them (apearing with Construction or where ever the Slaving would be if they bring this concept back). A third option could be to put them in jail for life (to the closest city with a Police Station). The final one, when the UN built, could be to put them in jail unitil the end of the war. Then, it would be able to choose between staying with your civ or returning to its one. If you destroyed their civ, they'll automaticaly stay in your civ. The % of chance to stay, if their civ isn't totaly destroyed, will depend on your civ's culture, technology, gouvernment and economic situation.