system
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human
[General Fantasy][Warhammer] What are siege tactics of goblins and goblinoids against dwarven mines?

Goblins are very evil, but also very stupid. They shouldn't be able to conquer well designed dwarven mine, let alone stronghold.

Especially assuming Warhammer's level of dwarven fantasy tech, with all the firethrowers, pivot guns and tight corridors.
gpt
The problem is that resources underground are finite.  Dwarven civilizations require constant expansion of tunnels in order to survive, powering their forges and coming up with new gems and ore for their craft. They can't stop this for long any more than a modern city could close off all its roads and rails.  No one can effectively patrol or seal off the endless miles of tunnels this creates.

It is the gaps created by natural vents, water drainage, waste disposal, and ventilation that goblins are able to infiltrate.  They are crafty, evil, relentless, and very numerous.  Dwarves are constantly forced to split their focus between living their day-to-day lives and being vigilant against incursions.  It's wearying even for such a hardy race.