Hear the story of Isakudip, Splatteredsyrup, the Undying Fortress!
I set up a fort at the border between a mountain range and a broadleaf forest. Workshops set up, stockpiles filled, everything was fine until at around a population of 30 (which came after the first immigration wave!), the a goblin necromancer arrives with a small guard and around 20 undead goblins. My whole military consisted of 5 axedorfs in training (with wooden axes) and 5 marksdorfs also in training, the best armor anyone had was leather. So I emergency-drafted EVERYONE in the fort and sent them charging the invaders. It was a slaughter and the fortress was depopulated in a matter of days.
An expedition was sent to reclaim said fortress, outfitted with metal armor, metal maces, a breeding stock of war dogs, a few meat rations and nothing else. The whole contents of the fort were found scattered, but no sign of the invaders. Sustaining on collected plants, these seven dorfs spent about a year tidying up the place, waiting for the first migrants to get the fortress running again.
That first wave was about 30 dorfs strong and after finishing reclaiming and collecting every single item and storing it, great stone coffins were erected in the main hallways to hosue the remains of the fallen of the first population. Security measures such as drawbridges and a walled-in outer yard were built and a small vile force of darkness (10 goblins) that arrived 2 years after was just sat out until all those visiting humans and elves took care of them. In the meantime, marksdorfs and macedorfs trained to be a force to be reckoned with. The fortress was thriving.
Around the 4th year the undead arrived again, around 20 undead and a handful of living goblins. The dorfs, confident that their fully metal-clad squad of mace-swingers can handle a couple of undead goblins, charged in with backup of 20 trained war dogs. Horror befell the attackers when, contrary to their expectations, they suffered great casualties and were wiped out to the last dog. The marksdorfs took the remaining dogs and attacked, but had little success. There were around 8 undead goblins left.
Remembering the brave souls that came here before them, the remaining dorfs took up arms (literally, since there were no weapons left to equip) and stormed at the undead army at their doorstep, beating them with their bare fists and dying glorious deaths, until the last remaining combatant, the mayor, finally slew the last of the undead and sunk down unconscious at the bridge leading to the inner fortress. Only one other dorf, other than children, was left. He nursed the heroic mayor back to health.
Only a few weeks after this epic battle, another wave of immigrants who had undoubtedly heard of this heroic place arrived and populated the legendary halls of Isakudip again, soon ungratefully electing a new mayor.
Soon after, ANOTHER vile force of darkness arrived, but as they gazed upon the battlefield that lay before them with smashed zombies and mangled war dogs, they decided to return to their homelands. You could literally watch them arrive and turn around instantly to flee the map.
The children of the second population are now growing up as well as the puppies of the war dogs that helped defend Isakudip during the Second Undead Storm, and a great memory hall reminds the current citizens that great bravery and sacrifice was all that defended their homes not long before they arrived.