In my previous fortress I didn't yet quite figure how fast animals breed if left alone. I brought plenty of breeding pairs with me on embark, and after discovering that a) milking cows isn't possible and b) butchering animals is a pain in the ass, I left them alone.
In the end I had a massive herd of 200 animals at my vagon. This was getting quite annoying, so I decided I needed something more organized.
I had my miners dig several small rooms into a separate part of the mountain face, with a hallway leading into them. Above the rooms, I channeled holes in each one and designated them as pit areas.
Once this was complete, I had the dwarfs haul the animals to the hole and toss them down to the room. Soon I had each animal type in a separate room. All of them naturally ganging up on the tightly closed doors. So I realize that I can't slaughter the animals without letting them all out.
Dissapointed, I leave the "barn" by itself and focuse on other things.
Some time passes and bang - my first goblin ambush! I'm getting slightly worried, as I haven't yet built any traps, nor do I have proper army. Doesn't look good for my poor dwarfs.
So I zoom on the ambushing squad to see where they are coming from.
Imagine my surprise when I notice that they are not approaching the undefended main entrance, but are instead inside the barn hallway, which is not even connected to the main fort.
So picture this: a full squad of bloodthirsty goblins skulking in an empty hallway.
Goblin a: "Gork, are you sure that diz iz the right way? Dez 'r no stunties around?"
Goblin b: "Imma sure, look at diz fancy masonry! Why'd anyboody build such a place, if notta keep dey gold and shinyes! Now open dat door before dem stunties spot us!"
So the goblin ambushers have made their way inside my fortress undetected, and they find a door that is not locked. And what ensues?
S T A M P E D E!
Seeing an opportunity to escape the murky cave they've been imprisoned in, the horses swiftly make their way towards the light... and right into the baffled goblin squad. Carnage ensues. Crazed horses make short work on the goblins at the door, kicking them to their deaths.
Goblins recover from their intial surprise, and start hacking desperately at the stampede, but there is simply too many wild horses. The ambushing squad is soon reduced to a handful of goblins that are bleeding all over. Unfortunately for the horses, they happen to be armed with crossbows.
The surviving horses are finally outside. They are free, they feel the fresh air blowing, they can smell the grass, they can feel the touch of sunshine on their manes... No more pain, no more darkness!
And then the goblins start raining death upon them.
Alerted by the commotion, the defence forces of the fortress reach the animal storage section. They are greeted by the sight of a severely wounded goblin crossbowman reloading it's crossbow at the entrance. The goblin doesn't even have the time to feel surprised as a wrestler swiftly crushes it's spine.
Last of the invaders dead, the scale of the carnage is revealed. 29 horses, all dead. 10 goblins, torn apart, their remains scattered out in the bloody hallway. Out from the hallway, bloody trail leads towards a tiny hill. Dead horses lay scattered along the trail. Behind the hill, the dwards find a single named horse foal, covered in goblin blood and unconcious. In a few passes of turns, he passes on, towards the heavenly meadows, where his brothers and sisters are awaiting for him.
"This is a masterfully engraved picture of Goblins and Horses. The horses are stricking the goblins down."