Well, there is really nothing special or even fancy behind the AI of the game. It's turn-based so there's no need for very fast routines and I also didn't use stuff like genetic algorithms or neural networks.
t's not easy to describe but basically it's some kind of finite state machine with a lot of randomness and the AI is personalized by setting different parameters (i.e. how big is the chance of attack enemies, how much of the income can the AI spent for military and civil stuff and so on). The AI also calculates priorities and risk factors for regions and will first take care of the endangered regions.

Initially I wanted to go for a neural network at a later stage but after implementing the above mentioned AI I noticed that it played well (and more important : each game is played different, so the player never knows how the AI reacts) and decided to stick with this approach.