Quote Originally Posted by itsme
PS. Why I can't play in campaign mode with Byzantee, but only with 4-5 factions ???
Its a way of trying to make sure players are familiar with the game by completing one campaign with the standard factions before unlocking the others. Check the M2TW Guides forum for how to unlock the other factions if you don't want to complete a campaign with one of them first.

Quote Originally Posted by itsme
Now one idea come to my mind i.e. I could tried to just pop-out outside the fortress so that he charge, but still !!!
Probably still wouldn't work or you would have to do it a lot to wear down an enemy with such a big quantity advantage.