war. Upon proposing a peace treaty, the president of proposing country is able to demand a certain sum of gold from the other country, however this is not a necessity.
Once the proposal has passed both congresses the war will end and if there's ongoing battles, defender will be declared as winner of the battle.
You cannot sign a peace treaty with your Natural Enemy: both countries must first unset Natural Enemy before they can sign a peace treaty. Once the Natural Enemy is set, it cannot be changed for 7 days.