Little is known of the early life of Blackjack, the pirate who became Aquaman’s most inveterate foe. He became publically known in December of 1941 when his ship, the Nemesis targets a pleasure craft in the South Pacific for theft.  After looting the safe, the pirate prepares to deep-six the crew starting by throwing the captain over the side.  Aquaman rescues him and in short order, routes the pirates back to the Nemesis.  Sending the pleasure craft home with the recovered loot, Aquaman leaps aboard the Nemesis.  After a brief scuffle, Blackjack downs Aquaman with a gas grenade.  Rather the kill the hero, Blackjack attempts persuasion, encouraging Aquaman to join his crew.  The war, he claims, sinks ships on both sides and leaves loot galore for those bold enough to take it.  Aquaman refuses and insults the pirate and is bound to anvil and tossed overboard.  Presuming the adversary dead, the pirate resume pursuit of the yacht and as they catch sight it, fire a torpedo to sink it.  Aquaman, having freed himself, catch the torpedo in flight and returns it toward the Nemesis.  Rocked by a terrific explosion, the ship begins to sink as Aquaman reboard it and makes short work of its crew.  The men flee and the Nemesis is lost but Blackjack is not found and presumed deceased.  In reality, he has made it to a nearby island where he swears revenge on Aquaman (More Fun Comics #74).

As it turns out, the island was inhabited by a small tribe of pearl divers.  Finding the exhausted Blackjack, the villagers revived him but realizing he was in a culture of pearl divers, murders the chieftain and assumes control.  He puts the villagers to work under threat of his gun but is unsatisfied with the quality of pearls recovered.  He orders the strongest young man Keoki to dive to the deepest beds under threat to his fiancée Loana.  Keoki attempts the dive but becomes trapped by a clam and nearly drowns before he is rescued by Aquaman.  Explaining his actions, Keoki convinces Aquaman to return with him.  Blackjack retreats with Loana, injuring villagers as he goes.  Aquaman eventually corners him and rescues Loana, turning Blackjack over to village justice.  The tribe anoints Keoki as the new chieftain and banishes Blackjack into the open sea (More Fun Comics #75).

Throughout the war,  Blackajck remained focused on operations as a pirate and had no truck with Axis forces.  He impersonated the Rajah of a fictional Arab state to kidnap the daughter of a prominent senator He was thwarted by Aquaman, leading to his first arrest (More Fun Comics #77).  Months later, he breaks free of his prison and gets hired as crew on a luxury yacht.  He manages to entice the crew into mutiny and cease control until Aquaman shows up and strands him on a desert island (More Fun Comics #80).