Well.
That was sure a convoluted way of getting my fortress to die.
So, I'd reclaimed the fort with the frozen lake that unthawed immediately on embark, killing everybody. I dig in, do well for a year or so, and Bam! Goblin siege. I fend it off without much difficulty. The lake cut off most avenues of approach, and I had dug a channel across the land bridge to my fortress entrance, and put a drawbridge across it, made raiseable to help shield dwarves from, say, crossbow goblins. This was the fatal mistake, as, after a few enjoyable rounds of Goblin Catapulting, I ended up with a chasm full of mace goblins with nowhere to go. Then the next siege arrived a season later, and the Master showed up with his cavalry troops. I wanted to take him prisoner, so I tried to raise the drawbridge to cut him off from his troops until he hit my cage traps. However, for some reason my lever dwarf was more responsive than ever before and instead raised it before the Master even stepped on the bridge. So I lower the drawbridge, but he steps under it on his war jabberer, causing the bridge to break.
Now I can't get out. After the siegers get bored and leave, my dwarves refuse to rebuild the bridge, because of the moat full of injured mace goblins from two sieges ago. Meanwhile, merchants show up just as the siege ends and immediately get ambushed by more goblins! So now there's weapons all over the map, and I need them for my weapon trap lineup. But I can't reach them! I start a project involving a ballista to shoot those mace goblins, but my dwarves have learned to detect goblins from around corners, and can't be convinced to dig the fortifications I need to actually hit the bastards.
Then winter hits. Suddenly, my dwarves can reach all those goods the merchants and ambush goblins left lying around, and mass stampede out to them. I try to convince some to finish building a lake wall intended to prevent goblins from just charging across the frozen lake, but they'd rather do a little dance:
1) Cross half the map, climb the cliff to reach the weapon bin someone dropped.
2) See the mace goblins from across the screen.
3) Scream like a little girl and drop all their stuff.
4) Decide to reclaim their dropped stuff.
5) GOTO 2.
This keeps the entire fortress busy, except for the one dwarf who I'd forgotten was mooding and apparently couldn't find an item he wanted. He, appropriately enough, went berserk and killed the fortresses' entire supply of animals while the others were out, before succumbing to a torn out throat.
And then: The third siege in three seasons arrives! They do exactly what I was trying to build a wall to prevent, rampaging along the ice and clogging the preliminary traps with the corpses of their fallen. I'm desperately hoping for spring to arrive before the second and third waves arrive, but it is not to be. They proceed to massacre everyone in the fort, leaving me with three survivors. The goblins come rampaging out of the fort to hunt them down.
Then Spring hits. Hilariously, three quarters of the goblin army is now drowning!
Sadly, so are all three of my dwarves.
And those blasted macegoblins are still stuck in their stupid trench, having caused all this stupidity by just standing there and making faces at my dwarves and grinding all progress to a halt, and I imagine they're just laughing and laughing...