Percival Plazchek (or "Percy Playboy") was a very rich but troubled youth in the 1940s. He held a secret hatred of his sister Joye since their father had named her as his heir. In January 1942, Percy donned an experimental armor that gave him the ability to control magnetic fields in a secret underground lair. As "Nuclear, the Magnetic Marauder", he attacked a U.S. warship, which led him into battle with Hippolyta – the 1940s Wonder Woman – and other members of the All-Star Squadron. This battle seemingly ended with Nuclear dying in a fire below his own playboy mansion. A few years later, Nuclear returned and extorted money from Lemuel Tugboat, owner of the Lenard Shipline, and hi-jacked one of Tugboat's ocean liners. Hippolyta and the All-Star Squadron once again stepped in to save the day and defeated Nuclear, he apperantly fell to his fiery death in All-Star Squadron #16.
Nuclear survived his supposed fiery encounter with death. Nuclear, Reactron, Neutron, Professor Radium, Mister Nitro, and Geiger would be sent by Luthor's Society to discern the leak from Bludhaven. They would come into conflict with the government team of Shade. They would call themselves the Nuclear Legion.