The film is largely based on A Princess of Mars, the first novel to feature John Carter. It was originally serialized from February though July 1912, in six monthly issues of the pulp magazine All-Story, under the title Under the Moons of Mars, and then those chapters were collected as a hardcover book in 1917. In the novel John Carter is a former American Civil War Confederate Army captain who is mysteriously transported to Mars, known to its inhabitants as Barsoom. In the course of his adventures he learns that the planet is dying from the loss of its atmosphere and water, and that only a peaceful alliance of its intelligent inhabitants can save all the species of Barsoom from extinction.