While I can't say 100%, everything that would add war weariness to your rival will give you half (killing units, taking cities, plundering trade routes, not 100% sure about liberating cities though), that is how it is right now, and and I have to say it makes vassaling anyone on huge maps a very very hard task.Every war weariness? Even trade route plunder?
Despite this, I've seen some civs in game go crazy, but I guess they can afford to neglect supply for some turns.