It comes as no surprise to me that my bloodiest siege was infact, my funnest, in both senses of the word.
I was playing with relentless assault, in a nice area with a volcano, flux, sand brook etc, and as such had been doing rather well on trade, which meant that the my fort began to be noticed. There are many races that siege you in relentless assault, but the most persistent for me where the lizard men.
Lizard men are pretty much like goblins, but come in larger numbers, use mostly copper weaponry, and are better at unarmed fighting.
In my first year a token force of 30 or so where defeated by my well trained military, and a few caged in traps so i could throw them into my death pit. The next year, however, was the really FUN siege.
I didn't use traps in this fortress (apart from a few cage traps) so the whole defense pretty much rested on my champions and marks dwarfs. I had a fortress population of about 50 this time, with a squad of 5 marks dwarfs, and about 7 champs.
The lizard men returned in force this time, over 70 of them, with a dedicated squad of spear lizards and crossbow lizards, lead by local leaders. This wasn't going to turn out well. I stationed my inside the fortifications, and hope for the best.
It went well at first, a squad of sword lizards had been quicker than the rest and was closer than the others, and took enough casualties from our crossbows to flee, however the rest of the squads where bunched close together, and advancing fast. The crossbow lizards where in front, but thankfully the fortifications where limiting their effectiveness, or so i thought...
The local leader shot a bolt through my fortification, hitting a champion in the heart and both lungs, then he shot another which hit one of my marksdwarves in the right leg. The other squads moved forward as well, unfazed by any bolts being shot at them.
They quickly took the doors and began fighting with my outnumbered champions, blood and viscera splattering the walls. Even the dwarf with pierced lungs and heart managed a kill before he dropped dead. Soon after, another champion was killed by the sword master, and i decided that for there to be any hope of surviving this siege, i would have to retreat and try and regroup my few forces, recruit a few civilians etc.
I ordered my dwarves to fall back, and they obeyed, except for the one marksdwarf who had been injured in the fight, who refused to move. What he did during the battle pretty much saved the fortress. He stayed at his post, shooting the crossbow master and another dead, before being ganged upon by lizards. In the time they took to kill him, my forces where able to escape and begin to regroup.
The lizards moved down a z level, and advanced down the hallway, killing any civilians they saw. Even then, the few defenders left refused to give up, a marksdwarf and a female wrestler, with her baby still in her arms, turned back and began shooting and attacking the advancing lizards. Both where quickly overcome and killed, the females baby being knocked several tiles away and splattering against a wall.
However, these displays on heroism had their effects, and the lizards for whatever reason, decided to retreat.
At the end of it, my military was pretty much annihilated, and my fortress succumbed to tantrum spirals.