How do you get the army you want in place for a given task?
I am supposing you know you want to get attack force to fight a supposed force of X in a given square. The high level AI also knows it must defend some spots. How does it know it can move some units from a previous attack, but shouldn't move units defending a city? Should it build units, and of what kind?
All decisions come down to:
1) What is my ideal units orders/builds for my goal? Ask for that budget.
2) Given a budget, do what I can.
Considering (1/budget), the question is:
Q1) Do I need new armies or can I move around existing ones.
Considering (1) and (2), the question is:
Q2) What units do I need (transports, artillery, infantry???)