I just lost my second fortress.
Got a goblin ambush (or siege, don't know what it was), so I activated my drawbridge and accidentally locked half my fortress outside. I thought this was the best plan of attack, as my military was very weak (I didn't have a sedenmentary layer or tin, so they had copper gear). Turns out the goblins didn't arrive till much later, when like 80 of my dwarfs had died because of the tantrum spiral that happened after half my fortress had to spend multiple nights outside in a snowstorm without water.
And when they arived, the remaining ~20 dwarfs where all to busy tantruming to pull the bridge back up, turning my entranceway red.
Needless to say, I facepalmed pretty hard.
So I presume the goblins arrived to an open fortress with 80 frozen dwarfs, and went inside to find 20 dwarfs beating each other up, shaking in the corner or smashing their own head open on a wall?
Actually I read some more things on the wiki, and apperantly, when the goblins came it was an actual siege.
So what happened was, I got a message about a goblin ambush. All my dwarfs ran out of my fortress for whatever reason, so I quickly pulled up my drawbridge, moved my military there and waited for the goblins to show up...
But no goblins came! (I think that my civilian dwarfs took care of them) So basically I ended up panicking and leaving half my fortress outside, in a snowstorm, without anything to drink. Needless to say, the combination of snow, having to sleep on the ground, the sun, thirst and dwarfs dying of thirst caused a tantrum spiral. The thirst problem only got worse because I had ran out of booze, and my dwarfs died of thirst before they could drink the newly brewed booze.
And to top it all off, a goblin siege arrived when I had just about 20 miserable dwarfs left (half of which also where insane)