I'd imagine it could work the same. A random amount of objectives and time allotted could be assigned based on map size and number of troops involved. Furthermore, the goals can be semi-randomized as well where you can have capture the flag (one side holds the objective(s)), encounter (where both sides hold none or some of the objective(s)), city capture/defense, or simply search and destroy (no objectives, just ram yourself into the enemy. Presumably you can even have phases that allow nearby reinforcements to join the battle as well as expand the map and change the goal/objectives on the map. Winning, drawing, losing can also have differing effects on the campaign map outside of one army runs away and the other doesn't.