A suggestion,. Cool downs have been discussed but that would leave lower players at the mercy of the few money players. A compromise could be:

* If the truce agreement is broken for attacking another player, then a cool down should apply.

* Cool down time does not need to be a long time, just enough for player to attack back. This gives time for alliances to rally against a larger player.

Truce agreement expires you should not have a cool downtime.