I got sieged moments after the fall caravan showed up. One trader lost the race to get into the fort, but most of them made it. So far so good. Well, as soon as the trader left outside bites it, the rest pack up and head for the exit, that is to say, the trap hall that I had just opened up to chew up the seige. So I close one door and open the other, to get goblins and traders to run to the other side of my fort. I try to lock the stupid traders in the far hall for their own good, but one makes it out and gets slaughtered.
Now I guess I have to back up a minute and say the far hall exits into an above ground keep with my archery range inside. I had cleverly thought to conserve arrows with one of those "trench around the targets" type dealies. Well now I know, those things are stupid unless you are desperately short of ammunition and even then, do they ever restack the arrows? Anyhow, I called up my new crossbow squad to position them at the head of the trap hall, where the ballista is going to go whenever I manage to get three masterwork parts. But I guess the squad needs ammunition. And where do you think they need to go to get it?
Into the courtyard.
And because the traders are locked into the other hallway, the only way into the courtyard is through my now activated spikes and drops hall.
I just didn't see them in time. And I put only dwarfettes into my crossbow squadrons, so of course three of them were carrying babies.
Oh Gods, there's baby parts everywhere.