After my first militia commander killed himself because some magma flowed out of the magma forge he claimed, my next commander was getting pretty decked out, and I sent her squad out to wait as some sieging goblins were funneled to the main route to the fortress through a 1-tile wide brook-finger. Of course as soon as the dwarves saw goblins marching up the brook, they charged forward without waiting even for their own group to all get together.
Somehow the commander was off by herself halfway across the map, carrying out an initial order to kill the enemy general (I wanted to fuckin get that guy). Separated, alone, and between two enemy squads in a narrow unclimbable brook canyon, she was butchered by halberds. She managed to bite off the general's nose and break his leg with a hammer. There was a long file of goblins between the 9 remaining of her squad and the fainting, retreating goblin general, and the dwarves were busy killing the goblins who fell unconscious in the narrow ravine, by slashing their elbows and feet repeatedly. The goblin fodder troops were killed, protecting their leader with the mountain that is their lame flesh, and the enemy general escaped with two wounded spearmen, missing a nose and dragging his leg.
I checked the goblin civ after a few months of game time, to see what leaders were left because I was itching for a new ambush, and the goblin general was no longer listed as a leader of their civilization. I wondered if he died from his wounds so I copied the save and looked in legends. In 550 Xuspgas Ruthlessclout became the general of the Enjoyable Hatred. In late spring 558, he led the attack on Shipwash. In late spring 558, he ceased to be the general of the Enjoyable Hatred.
They didn't replace him with anyone. I wonder if he had to retire from wounds, from the shame of his disfigurement, or if he had done all he wanted to do. As far as I know he disappeared, likely fallen unconscious and kicked in the lungs by bogeymen or spammed to death by small animals.