Once had a large population of elephants outside my fortress. Set up some cage traps, caught around 8 in total. 6 were made into war elephants. Little did I know that in the last two there was the spawn of satan.
Had a bunch kept near the trade depot, still in cages being lugged from the outside. I built the cages and released them. Suddenly:
"URIST MCMINER CANCELS EAT: INTERRUPTED BY ELEPHANT".
Apparently two elephants weren't tame. Oh fuck. Since I liked my elephant armada, I thought I'd rather catch them again and tame them. Apparently the dumbest of the two tried to kick a miner, who proceeded to beat it to an inch of its life. It had easily 10+ broken bones and was laying in a pool of blood and vomit. I thought since the one was already pretty much dead, the other should die too.
Big mistake.
It was currently inside my workshop space (Which was in a cavern surrounded by an underground lake). My only form of an army, my militia commander and his war elephant, chased after it. Militia commander hacked it a few times as it ran, but only chipping bone and bruising fat. It ran, bleeding, around the fortress like crazy, then returned to the workshop level, where the hospital was. It ran into the narrow hospital corridor, and I knew it was over. No place to run. It then proceeded to beat the everloving shit out've the militia commander, before his elephant could arrive to help. In one last defiant act, he cut off the elephant's left ear. The elephant retreated back into the hospital and beat the expedition leader, who was just passing through, to an inch of her life, leaving them both with a broken leg and arm each, as well as lots of bruising. Beaten but alive.
The elephant was now hanging out in a tiny part of the cavern that was on a lower level, near the lake. Its presence meant that the injured could not rest. Remembering what the miner did to the other one, I quickly drafted one and sent him after it. He chased it back into the hospital...where it proceeded to, in one move, dislocate his spine with a kick, and leave him slumped against the hospital wall, crippled. Next plan of attack, naturally, was to recruit the OTHER miner. He chased the elephant toward the carpenter's shop, cornering it. Only striking it a few times in the leg and the chest, the miner was quickly beat to death, his skull caved in. This is when the demonic elephant gained a name: Lovelycircles. As a last ditched effort to bring her down, I recruited the woodworker, armed with a copper axe, and assigned two war elephants to him.
They chased her back into the hospital (WHY OF ALL PLACES?!), with the woodworker entering the main part and the elephants lagging behind in the hallway. This was her attempt at an old trick, to go around her attacker while they were inside the hospital. It had worked on the militia commander, but not the woodworker. She ran directly into the waiting elephants, while the woodworker attacked from behind. Lovelycircles, already weak from old injuries, tried to attack the woodworker, who dodged, and the three proceeded to beat her to death. She died in the hallway of the hospital, surrounded by three victims she crippled for life. The miner would make a full recovery, while the militia commander was crippled until the end. The expedition leader died, sadly, to infection shortly after the death of Lovelycircles.
It was this elephant that brought about the fort's destruction. And I had thought they were not capable of Boatmurdered-grade destruction in DF2010. Boy did I learn the hard way.