I don't understand at all, why would anyone do this? To build a city instead of one, a city that you want? And is it worth it?
1) With a secondary, small army, you take the main castle of the enemy (the main thing is to sneak up on an unprotected castle:)). While his main army is running to the castle, there are, on average, 2-3 days, during which you can destroy almost all the dwellings. And it turns out - a weak hero deprived the enemy of an army and money.
2) A neutral castle of another race. It is very convenient to convert it into your own castle. (especially if there are external dwellings)
