John Thornton: A compassionate, wise, sensible man who always craves another adventure. Bearing the greatest resemblance to the author in character and in name (Jack London's given name was John London), John Thornton rescues Buck from Hal's cruel whip, nursing the poor dog back to health. Buck grows to love this man because of this kindness, helping Thornton in turn when he is drowning in a river, when he is attacked by another man, and also when John makes a bet that Buck can pull a sled weighing half a ton all by himself. Thornton then takes Buck on a new adventure for gold in the Yukon Territory, although he is killed by the Yeehat warriors while Buck is away hunting moose in the forest. Upon returning to the camp, Buck slays these dancing Yeehats in rage, mourning for his dead friend. His love for Thornton had always been stronger than the call of the wild; however, with Thornton dead, Buck reenters the forest and joins a wolf pack, living life from then on as a wild beast. Judge Miller: A wealthy, retired judge who owns a spacious estate in California's Santa Clara Valley. Buck's St. Bernard father had been Judge Miller's devoted companion, and Buck succeeds him in fulfilling this role. Compare
Thornton saves Buck from death at the hands of Hal, and Buck rewards Thornton with fierce loyalty. Thornton’s relationship to Buck is the ideal man-dog relationship: each guards the other’s back and is completely devoted to the other. Judge Miller was Buck’s original master, the owner of a large estate in California’s Santa Clara Valley. They were devoted to each other as well.