Rebel leaders could be main characters in a World War 3 game story. They might be fighting against an oppressive regime that is part of one of the warring factions. These rebels could be from areas that have been marginalized or exploited. Another type of main character could be scientists. In a world at war, scientists could be working on developing new weapons, or they could be trying to find a way to end the war through some scientific breakthrough, like a new form of energy that could make the fight over resources obsolete.