Well that's the end of this fort.
An incredibly fast, incredibly powerful Spider Titan from the mountains attacked my fort. It slaughtered my entire military when I sent them after it, then after I closed the main gate it found its way through my underground water reservoir, then into a channel which lead straight to my medical bay.
Shortly after the fall of my soldiers:

Oh and this was just after the elves launched a siege against me which I just barely defended, and about 5 minutes after the titan spawned goblins also launched a siege. Somehow the titan scared the goblins away or something, because after the titan killed two of them the entire army ran and left the region.
The 3 storage areas outside to the right are for dead things. Ran out of dead thing storage inside the fortress. :P
Also the stones are there so my masons could work quicker when they were building the walls. Never got around to removing them.