Complex sentence: When the Horsemen of Apocalypse attacked Manhattan during the events of the "Fall of the Mutants" and caused a blackout, a Vietnam veteran named Ammo organized a gang including the Wildboys, who looted the city.
Split into simpler sentences: When the Horsemen of Apocalypse attacked Manhattan during the events of the "Fall of the Mutants" and caused a blackout. A Vietnam veteran named Ammo organized a gang including the Wildboys, who looted the city.