I have crossed several players who offer you an alliance. Once the alliance has been accepted, they come and smash you 'in the belly' (in the your strongest position) in order to destroy when the alliance is still on. You would expect to be able to rely on your ally. In my humble opinion, this kind of behaviour kills the fun of the game, would it be possible to implement a button to report 'unreliable allies' please?
Let's consider player A and player B become allies.
When player B wants to break the alliance, he presses the 'break alliance' button before any attack.
It is only fair to stop the alliance before any attack/betrayal.
This would also make the difference between 'fair play' (or normal course of a game) and cheating/abusive action.
Saying more on this idea.
Stopping an alliance is part of the game but you should stop the alliance (using the alliance feature feature in the game) in order to act that the alliance is over before actually turning your ally into your prey/enemy.
Players would be required to end the alliance before attacking allies.