Incredibly realistic.
The main reason I liked this game is the feeling you don't gather resources, the way this is handled is by capturing fields on the map that increase your bullet and oil supply. Another pretty cool touch is the role of a good cover. If you start shooting while out on the open you really risk much. On the other hand if you hide in a house and the enemy happens to have a cannon or a tank you have to get of there very quickly. The enemy AI is very good, they will try to flank you or even avoid you if they want to achieve something else other then kill a couple of your troops. All in all you have to think your actions through, because just massing troops and launching an attack will not get you anywhere. All in all, a must play.