[scorpio_rocks]

The game will end when either it reaches the last turn (battle length shown bottom of screen) or if the AI cannot possibly win, ie no more units due to arrive, you have all Victory Hexes, all units in rout or worse, etc.

If you have captured all victory objectives and killed/routed all AI units, then chances are it has reinforcements due and game will end when these arrive and AI sees its hopeless.

In a wider sense the battle type doesn't affect how to "end" the battle - kill the enemy and capture/hold the objectives. The batte type really only affects what forces are available and how prepared they are.