This then randomizes how you approach each battle, because your leaders are only really effective when commanding their own unit type. Battles beyond the first in a campaign use your original forces plus randomized additional units against another random set of enemy forces. The nice thing about this is that it creates the effect of you not knowing exactly what your enemy's strength is. With the Generator, all of the maps from the game can be used, as well as generic maps of different terrain types, as wells as maps of specific cities or regions. While the maps themselves cannot be altered, all the other variables, including the weather, can be.
Weather can have a significant impact on how a game plays out.
The addition of rain grounds fighter and bomber aircraft, making it hard to soften up those stubborn entrenched targets. Rain seems to affect the movement rates of some units, but without a clear definition in the manual, this is just an educated guess. Snow severely effects all movement except road movement, so be aware of this in scenarios with snow. Fog has the effect of reducing the effectiveness of artillery and air to ground attacks, but again that is my best estimate of the result, since it is not in the manual as far as I can see. Other variables in the Battle Generator include troop and leader quality, number of turns, starting date, available roster slots, and nationality.