You know how the alliance page and the alliance wall provide players with information regarding friendly alliances? There's a slight problem with this when players are searching for res and don't check the information their alliance provides.
Could there be a green smiley face placed on friendly cities, so that players will have a visual cue? Or at least have a window pop up asking, "Are you sure you want to break the truce with this alliance?" And maybe if the player clicks "Yes", then the OL gets an in-game mail about who is risking the truce?
There's a similar example of something like this already in the game. The blood pact bubble will inform you if you're about to "pop" it by attacking another player.