Lincoln County War - 1878 - Billy was involved in a conflict over land in New Mexico between cattle barons John Chisum and other ranchers - Chisum had a huge ranch and settlers and other ranchers were desperate for land - conflict broke out between the two sides, Billy's on Chisum's side against Murphy - the war ended with Murphy's death but one of Billy's friends had been killed - Billy swore he would kill everyone responsible for the death of his friend in the war