Abraham Lincoln Kieros was a mutant with the ability to create explosions by clapping his hands. As the result of war injuries, Kieros was paralyzed from the neck down and forced to stay in an iron lung, barely able to speak. One day, Apocalypse came to him, deeming him worthy. Apocalypse restored his health and made him his second Horseman, War.
After being transformed into War, Kieros, Pestilence, and Famine battled the X-Factor in Central Park and were defeated by Iceman. After the fourth Horseman, Death, was revealed Apocalypse had the Horsemen battle each other to establish a leader. Death beat them all.
After Apocalypse teleported X-Factor on his Celestial Ship, they battled the Horsemen again and, after their defeat, the Horsemen were sent into Manhattan to incite chaos. X-Factor and the Power Pack battled the Horsemen, Pestilence was killed, Famine was sent to America's Bread Basket, and Apocalypse called War and Death back to Ship, where Death rejoined X-Factor and X-Factor defeated them.
War, Famine, and a new Death kidnapped Jean Grey and Cyclops and handed them to Mr. Sinister, who duped them by disguising himself as Apocalypse. The X-Men and X-Factor sought out the Horsemen and defeated them.
Later, Kieros was left in his injured state, until Angel, the former Horseman, Death, healed him with a new energy obtained battling the new Death.
Abraham Kieros was selected by Apocalypse and transformed into his Horseman War.
He fought alongside the other Horsemen when the X-Men sought out Apocalypse’s Lazarus chamber.