Built a nice little enclosure between two tombs (DFHack aided), so that when the inevitable zombie siege hit the only thing to do would be to pull down the inner ramps. Not much of a security feature, I know, especially when the staircase to the caverns is outside the walls for some inexplicable reason. It's not like I forgot about it either, because there was a wooden hatch over it for security
Anyway, inevitable zombie siege occurs as the first human caravan is trading. Sealing the fortress off and trying to rescue the five dwarves in the caverns actually goes pretty well, with only three fatalities. Could have been zero, but a lone goblin ambusher was already on the map and had sneaked through the hatch, rendering it unlockable. So, I quit and decided to see if I could save everybody. Several times. Nope!
Dwarves are extremely persistent about going places. One dwarf was in the middle of returning a gathered web when the siege hit, and to get him to drop the damned web and go get stationed without trying to return it to the loom I had to do the following:
:cancel the job via the jobs screen.
:forbid the web/thread.
:wait for the dwarf to drop the thread.
:once the dwarf is not holding the thread and has no job, then they can be stationed.
Also, it seems that disabling supplies after you put a dwarf in a squad will trigger a Pickup Equipment job for a waterskin even if you don't leave the military screen, and a dwarf cannot be deterred from heading to their original job target.
In the end, the would-be weaver died because something else drew him up the stairs. I believe he may have been following the civilian alert I briefly put in place to make sure everybody was the right side of the walls when the ramps were finally removed, since dwarves can't be dissuaded from doing that after they've started. In doing so, he reclaimed the hatch and saved the lives of the other four dwarves down there. They are locked in with a lone bulgy-eyed macegoblin who'd rather not be there and have no picks, no axes, no wood, and five units of alcohol between them, but at least they're alive.