>>279645183
I think it's exactly like the story said. War scientists tried to invent some new bacterial weapon and ended up synthesizing a germ powered by the souls of the dead, which then slowly built their "conquer the living world" kind of plot by using the machines+fishes and later on the humans+fishes.
The "stench of dead" isn't just how a rotten corpse smells but literally the stench of the living dead (ghosts).