I advise you to try it when you are working with AIAndy's coding and you'll see what I mean - it brings up a huge list of functions all called the same thing but differing only by the input of the parameter type and I might be getting better at following that sort of thing now but its still a pain in the ass. There's 2 steps to a unit AI. 1) how does it come into play - when and why, and 2) where is it going to be used and how. The AI does keep minimum amounts of particular UnitAI types in its cities usually - depends on the type. Excess to that does go elsewhere where demand exists and it even measures that demand against the time it will take for the unit to get there, how many other units have answered the call already, that sort of thing. There's a lot to it and it's fairly similar to what you said. When the city goes through figuring out what to build, it is also figuring out what it specifically most needs (and considering national needs along the way.) Whether it needs a property control response (building/unit/help from elsewhere etc...) is a checkpoint it makes at multiple junctures on that decision path and it is supposed to start off fairly tolerant and grow more and more demanding as it gets more and more on top of its needs and wants... I just ended up adjusting it to be far more demanding than it should be right up front.