Is there a way to deal with them ?

I got 4 at a time and only one general to take them on!

I was forced to turn invicible kingdom on and it ruins all the fun of managing it...

Kill Troll king, this isn't a war you can win by just waiting it out. You need to go kill their leadership or else you will lose the game.

Yeah my problem was that I waited too long , I managed to kill him and now I'm back on track :)