Okay, here is an example of what I am talking about. In RTI French and Indian War, Washington's command is holed up in a wooden fort, assaulted by a two-"stack" French force that outnumbers them 3-1. Washington's make a good fight; French knock down a couple of sections of wall, but British troops repel first two charges, despite running out of ammo. At this point, the AI get's confused and starts running troops back and forth; I decide to simply fast forward to the end of the battle and claim the (mostly deserved) victory.

Now, at the end of the battle, while several French units have routed, the French still have probably half a dozen non-routed infantry regiments that are still between 25% and 50% strength, plus at least one battery of artillery that is solely intact; all in all probably at least 400 men left on the field with decent morale (and not counting a similar number that have routed off the field alive). The Relative Strength bar is still noticably in France's favor When I go to the after battle screen, however, the game has somehow decided all those men are dead, at that the French army only has about 100 men alive. And then, of course, it decides that those 100 men are not enough to sustain their units, and the whole stack dies. So out of 1900 men in two French commands that had at least 400 men (and most probably more) get off the field alive, and against a enemy that was still numerically inferior at the end of the battle, the game simply decided to eradicate them all, giving me a free shot to Quebec.