So, I have a main entrance, in a valley, for caravans and whatnot, and two towers up on hills on each side. For lumber convenience, the towers have floodgate garage doors that can be opened. I leave them open unless there is a siege or ambush in progress.
A siege arrives. Fine. I send dwarves to flip the levers that'll close the garage doors on the two towers, so the only way in is through my main entrance, it's Bridge of Death(tm), drowning chamber, etc. I order dwarves inside, and deploy my military -- a squad of marksdwarves in each tower, and the wrestlers near the main entrance.
Watching the goblin's movements, I see they're going for a tower, not my main entrance. That's odd. I pause and investigate, only to find that the floodgates on one tower didn't close because someone's glove is lying on it. A glove. Dozens could be slaughtered because someone couldn't be arsed to pick up their clothing.
But maybe it's not so bad. I should have a squad of marksdwarves there. Look up near the top of the tower. A single dwarf. Where are the rest? Oh, they're eating. In the dining room. Halfway across the map. Despite the fact that I put a dining room and food supply right there in the tower, to avoid such a possibility.
Ok, ok. So a single marksdwarf is in the tower. Well, it was nice knowing her, but maybe she'll occupy the goblins long enough for the rest of the military to finish their meal, maybe have a nice after dinner dessert, cup of coffee, mint, and then get back to doing their jobs.
So I unpause, and watch. The dwarf fires off a few crossbow shots at the swarm of goblins converging on the tower, but then stops. I pause and find her. She's run out of ammo, and ignoring the plentiful ammo stockpile in the room with her, is descending the stairs. I figure, maybe she's hungry and wanted to get some dinner with her mates.
Unpause. She skips the stairs to the rest of the fortress, and instead runs outside into the arms of the goblins. Double check: yep, dwarves are ordered to not go outside, but there she goes. Goblin arrows converge on her like drunks at closing time, but she keeps coming.
And then, boom, a goblin's dead. And another. And another. More arrows swarm in, but it's hard to tell in the sea of red letters. She's in the middle of a pack of twenty or so, and everything's flashing enough to give an epileptic fits, but suddenly the goblins are running in all directions, and she's chasing after them, throttling the ones that she finds with her blood, ichor, and vomit covered hands.
And then she's all alone, covered in the gore of battle, howling her triumph to the sky while she snaps the last neck in half before breaking the goblin's spine over her knee. Eventually, the rest of her squad makes its way from dinner to the tower, asks her what happened and if she had a nice time, and goes back inside.
Checking her profile, she killed seventeen goblins during that siege, entirely unassisted. I'd never seen anything like it.