From: Bramble Rose Farm, KS
AI uses rules. Often Leaders/Armies don't use their own rules. This could be that they don't know them. It could be they know them, and change them when they don't apply to the situation. On the other hand, an army might goose-step exactly through their countries stated doctrine. Depends on the day, the unit/organization, and the commander.
More often than not, real human action defies the idea of artificial intelligence. If you assume your opponent is a professional you will be surprised when he kicks your ass because/while being--he is an amateur; opponents are under no obligation to play by any doctrinal rules. Heck, they might not know what they are.
In my opinion, that's why people say AI's suck. An AI that attempts to portray a particular nation's doctrine is a tough task. Why? Because 80% of any army's leadership does not understand the task and purpose of any operation they are directing. They're pulling it out of their ass as each minute passes. Some are good at this, others are not.
Combat is not chess or checkers; it's bedlam. Sometimes you eat the bear, sometimes the bear eats you. The last one to make a mistake wins.