Fifty years after a nuclear holocaust, mankind is decimated and the surviving nations—the American western-influenced Market and the Soviet-Russian-influenced Confederation—have agreed to outlaw traditional open war. In their place, disputes are settled with gladiator-style matches between giant robots operated by pilots called "robot jox" who are contracted to fight ten matches. The Confederation champion is Alexander, who has killed his last nine opponents thanks in part to a spy in the Market leaking information to the Confederation. The Market's champion, Achilles has won nine fights and will fight his final match against Alexander for the territory of Alaska. Achilles is supported by robot designer "Doc" Matsumoto and strategist Tex Conway, the only jox to win all ten of his contract fights.
As Achilles gets the upper hand in the match, Alexander launches a rocket fist at him. The projectile goes out of control and heads toward the bleachers. Achilles intercepts the projectile but his robot takes the full force of the impact and is knocked into the crowd, killing over 300 people. The referees declare the match a draw and order a rematch, but Achilles, shaken by what happened, declares this was his contractual tenth match and announces his retirement. He goes to live with his brother Philip and his family, and finds he is publicly branded a traitor and a coward. Meanwhile, a new jox is chosen to face Alexander, a genetically engineered "gen jox" named Athena, who is the first female jox. Worried for Athena and attracted to her, Achilles returns to the Market and agrees to fight Alexander again, infuriating Athena.
As Achilles' robot is rebuilt, Matsumoto refuses to divulge any knowledge of its new weapons so it cannot be leaked by the spy, and Conway confides in Achilles he believes Matsumoto is the spy. Conway confronts Matsumoto in his office. Matsumoto reveals he has analyzed Conway's final fight and deduced that the "lucky" laser hit Conway claims allowed him to defeat a clearly superior opponent was in fact deliberately aimed; Matsumoto accuses Conway of being a Confederation agent. Conway confesses and shoots Matsumoto, who secretly records the deed as part of the mission briefing. Conway informs the Market leadership that Matsumoto was the spy. On the day of the fight Athena drugs Achilles and steals his jox suit to commandeer the robot. Unable to stop the fight once she takes the field, the Market decides to support her. While watching Matsumoto's briefing on the robot's new weaponry, the footage of Conway killing Matsumoto is played and Conway jumps down the robot's elevator shaft to his death. Alexander takes the field against Athena. Athena takes the early advantage, but Alexander overpowers her and incapacitates the robot. The fight is declared in Alexander's favor and referees order him to stand down. Achilles arrives on the field and takes over the robot from Athena while Alexander smashes the referee hovercraft; the two jox stand to continue the fight. Both robots take to the air and a short space battle ensues. Alexander critically damages Achilles' robot, forcing him to crash land and flee for cover to the arm of Alexander's robot Athena sliced off earlier in the fight. Achilles hotwires the arm to launch its fist at Alexander, destroying his robot. Alexander emerges from the wreckage and the two battle with poles before Achilles finally convinces Alexander a match does not have to end with the death of a jock. Alexander throws down his weapon, and they salute each other with the jox's traditional "crash and burn" fist bump.
