This map was designed to build up your "economy", defences and your defensive army, and then, when you think you're ready, press the F1 button (version 1.2 is needed) and try to survive the biggest siege ever (I'm talking about some hundreds of swordsmen, pikemen, crossbowmen, etc...). The only problem about that is that to have so many troops to siege your castle you'll have to wait till the previous die, as the game only supports a limited number of units for a map (about 2000, but I'm not sure) so if you reach the limit and keep invading, there simply won't appear any units. Ok, good luck (don't forget the pitch diches!!!).