If you need to take a rival town down a notch or two, you may declare war during your Attack Phase. Pick some or all of your Troop cards to send to the attack.
The defender may pick some of their Troop cards to defend. If the attacking strength is greater than the defending strength, that’s how many VP worth of Building cards are lost. Use the printed value on each Building, ignoring any bonus VP another card might give it.
The defender chooses which buildings are lost. You can’t destroy half a building in this game, so – for instance – if 3 points of damage gets through but all the defender’s buildings are 2-pointers, only a single building is lost.
If the defending strength is equal to or greater than the attack strength, no buildings are lost.
Note that some buildings give bonuses to combat values!
After that, all Troops committed by both sides are discarded! This means that each Troop card you buy will be used in only one battle. It also means that you may choose not to commit some cards, like the Sage, to battle. Their special powers are worth more than their combat value!
Note that neither the attacker nor the defender must commit their whole army to combat!