Tactics for the Stronghold.

I just can't understand how 2 goblins + 20 orcs, after taking one crypt, can move on to another, and then to a dwarven stronghold. Well, you can take one building – it's your territory and all that. But after that, there will be losses. Let's take even a near-maxed-out crypt with 5 vampires. Apparently, those infamous goblins will immediately be sent as fodder to the vampires and ghosts, and they'll eat them. Okay, let's say the orcs didn't kill 3 vampires, but 5 (it happens). But in the second round, you can't just start attacking because skeletons and even zombies will arrive, so you need to do something else. There will be at least 2 orcs lost to the ghosts, okay, then they run away and kill everyone. Fine, they came out of the crypt with 18 orcs, and they only lost 2 goblins and 2 orcs (although that's quite an achievement, in my opinion). But how do you then go into another crypt? That's what I don't understand. Vampires and ghosts quickly overwhelm you, and even with a near-maxed-out crypt with 5 vampires, you can not only lose your army but theoretically even be completely wiped out. And after that, how do you even go into a dwarven stronghold? Maybe it's better to do it without orcs? Birds will take a crypt in one or two turns.