A clan may offer a peace treaty to another clan which means neither clan can attack any of their members. This lasts for as long as the clan's want, meaning it can be cancelled at any time.
When war ends, a peace treaty is forced on both sides, where players cannot attack each other for the next week. The hall of war allows you to attack the players whilst under a peace treaty, but the hall of peace causes the attacker to suffer from a 10% reduction in attributes. It also prolongs the time of peace.